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  • Variable Scope in C++

    A scope is a region of the program and broadly speaking there are three places, where variables can be declared −

    • Inside a function or a block which is called local variables,
    • In the definition of function parameters which is called formal parameters.
    • Outside of all functions which is called global variables.

    We will learn what is a function and it’s parameter in subsequent chapters. Here let us explain what are local and global variables.

    Local Variables

    Variables that are declared inside a function or block are local variables. They can be used only by statements that are inside that function or block of code. Local variables are not known to functions outside their own. Following is the example using local variables −

    #include <iostream>
using namespace std;
 
int main () {
   // Local variable declaration:
   int a, b;
   int c;
 
   // actual initialization
   a = 10;
   b = 20;
   c = a + b;
 
   cout << c;
 
   return 0;
}

    Global Variables

    Global variables are defined outside of all the functions, usually on top of the program. The global variables will hold their value throughout the life-time of your program.

    A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration. Following is the example using global and local variables −

    #include <iostream>
using namespace std;
 
// Global variable declaration:
int g;
 
int main () {
   // Local variable declaration:
   int a, b;
 
   // actual initialization
   a = 10;
   b = 20;
   g = a + b;
  
   cout << g;
 
   return 0;
}

    A program can have same name for local and global variables but value of local variable inside a function will take preference. For example −

    #include <iostream>
using namespace std;
 
// Global variable declaration:
int g = 20;
 
int main () {
   // Local variable declaration:
   int g = 10;
 
   cout << g;
 
   return 0;
}

    When the above code is compiled and executed, it produces the following result −

    10

    Initializing Local and Global Variables

    When a local variable is defined, it is not initialized by the system, you must initialize it yourself. Global variables are initialized automatically by the system when you define them as follows −

    Data TypeInitializer
    int0
    char‘\0’
    float0
    double0
    pointerNULL

    It is a good programming practice to initialize variables properly, otherwise sometimes program would produce unexpected result.

  • C++ Variable Types

    A variable provides us with named storage that our programs can manipulate. Each variable in C++ has a specific type, which determines the size and layout of the variable’s memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

    The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because C++ is case-sensitive −

    There are following basic types of variable in C++ as explained in last chapter −

    Sr.NoType & Description
    1boolStores either value true or false.
    2charTypically a single octet (one byte). This is an integer type.
    3intThe most natural size of integer for the machine.
    4floatA single-precision floating point value.
    5doubleA double-precision floating point value.
    6voidRepresents the absence of type.
    7wchar_tA wide character type.

    C++ also allows to define various other types of variables, which we will cover in subsequent chapters like Enumeration, Pointer, Array, Reference, Data structures, and Classes.

    Following section will cover how to define, declare and use various types of variables.

    Variable Definition in C++

    A variable definition tells the compiler where and how much storage to create for the variable. A variable definition specifies a data type, and contains a list of one or more variables of that type as follows −

    type variable_list;

    Here, type must be a valid C++ data type including char, w_char, int, float, double, bool or any user-defined object, etc., and variable_list may consist of one or more identifier names separated by commas. Some valid declarations are shown here −

    int    i, j, k;
char   c, ch;
float  f, salary;
double d;

    The line int i, j, k; both declares and defines the variables i, j and k; which instructs the compiler to create variables named i, j and k of type int.

    Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows −

    type variable_name = value;

    Some examples are −

    extern int d = 3, f = 5;    // declaration of d and f. 
int d = 3, f = 5;           // definition and initializing d and f. 
byte z = 22;                // definition and initializes z. 
char x = 'x';               // the variable x has the value 'x'.

    For definition without an initializer: variables with static storage duration are implicitly initialized with NULL (all bytes have the value 0); the initial value of all other variables is undefined.

    Variable Declaration in C++

    A variable declaration provides assurance to the compiler that there is one variable existing with the given type and name so that compiler proceed for further compilation without needing complete detail about the variable. A variable declaration has its meaning at the time of compilation only, compiler needs actual variable definition at the time of linking of the program.

    A variable declaration is useful when you are using multiple files and you define your variable in one of the files which will be available at the time of linking of the program. You will use extern keyword to declare a variable at any place. Though you can declare a variable multiple times in your C++ program, but it can be defined only once in a file, a function or a block of code.

    Example

    Try the following example where a variable has been declared at the top, but it has been defined inside the main function −

    #include <iostream>
using namespace std;

// Variable declaration:
extern int a, b;
extern int c;
extern float f;
  
int main () {
   // Variable definition:
   int a, b;
   int c;
   float f;
 
   // actual initialization
   a = 10;
   b = 20;
   c = a + b;
 
   cout << c << endl ;

   f = 70.0/3.0;
   cout << f << endl ;
 
   return 0;
}

    When the above code is compiled and executed, it produces the following result −

    30
23.3333

    Same concept applies on function declaration where you provide a function name at the time of its declaration and its actual definition can be given anywhere else. For example −

    // function declaration
int func();
int main() {
   // function call
   int i = func();
}

// function definition
int func() {
   return 0;
}

    Lvalues and Rvalues

    There are two kinds of expressions in C++ −

    • lvalue − Expressions that refer to a memory location is called “lvalue” expression. An lvalue may appear as either the left-hand or right-hand side of an assignment.
    • rvalue − The term rvalue refers to a data value that is stored at some address in memory. An rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right- but not left-hand side of an assignment.

    Variables are lvalues and so may appear on the left-hand side of an assignment. Numeric literals are rvalues and so may not be assigned and can not appear on the left-hand side. Following is a valid statement −

    int g = 20;

    But the following is not a valid statement and would generate compile-time error −

    10 = 20;

  • C++ Data Types

    While writing program in any language, you need to use various variables to store various information. Variables are nothing but reserved memory locations to store values. This means that when you create a variable you reserve some space in memory.

    You may like to store information of various data types like character, wide character, integer, floating point, double floating point, boolean etc. Based on the data type of a variable, the operating system allocates memory and decides what can be stored in the reserved memory.

    Primitive Built-in Types

    C++ offers the programmer a rich assortment of built-in as well as user defined data types. Following table lists down seven basic C++ data types −

    TypeKeyword
    Booleanbool
    Characterchar
    Integerint
    Floating pointfloat
    Double floating pointdouble
    Valuelessvoid
    Wide characterwchar_t

    Several of the basic types can be modified using one or more of these type modifiers −

    • signed
    • unsigned
    • short
    • long

    The following table shows the variable type, how much memory it takes to store the value in memory, and what is maximum and minimum value which can be stored in such type of variables.

    TypeTypical Bit WidthTypical Range
    char1byte-127 to 127 or 0 to 255
    unsigned char1byte0 to 255
    signed char1byte-127 to 127
    int4bytes-2147483648 to 2147483647
    unsigned int4bytes0 to 4294967295
    signed int4bytes-2147483648 to 2147483647
    short int2bytes-32768 to 32767
    unsigned short int2bytes0 to 65,535
    signed short int2bytes-32768 to 32767
    long int8bytes-9223372036854775808 to 9223372036854775807
    signed long int8bytessame as long int
    unsigned long int8bytes0 to 18446744073709551615
    long long int8bytes-(2^63) to (2^63)-1
    unsigned long long int8bytes0 to 18,446,744,073,709,551,615
    float4bytes
    double8bytes
    long double12bytes
    wchar_t2 or 4 bytes1 wide character

    The size of variables might be different from those shown in the above table, depending on the compiler and the computer you are using.

    Following is the example, which will produce correct size of various data types on your computer.

    #include <iostream>
using namespace std;

int main() {
   cout << "Size of char : " << sizeof(char) << endl;
   cout << "Size of int : " << sizeof(int) << endl;
   cout << "Size of short int : " << sizeof(short int) << endl;
   cout << "Size of long int : " << sizeof(long int) << endl;
   cout << "Size of float : " << sizeof(float) << endl;
   cout << "Size of double : " << sizeof(double) << endl;
   cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;
   
   return 0;
}

    This example uses endl, which inserts a new-line character after every line and << operator is being used to pass multiple values out to the screen. We are also using sizeof() operator to get size of various data types.

    When the above code is compiled and executed, it produces the following result which can vary from machine to machine −

    Size of char : 1
Size of int : 4
Size of short int : 2
Size of long int : 4
Size of float : 4
Size of double : 8
Size of wchar_t : 4

    Following is another example:

    #include <iostream>#include <limits>usingnamespace std;intmain(){


    std::cout &lt;&lt;"Int Min "&lt;&lt; std::numeric_limits&lt;int&gt;::min()&lt;&lt; endl;
std::cout &lt;&lt;"Int Max "&lt;&lt; std::numeric_limits&lt;int&gt;::max()&lt;&lt; endl;
std::cout &lt;&lt;"Unsigned Int  Min "&lt;&lt; std::numeric_limits&lt;unsignedint&gt;::min()&lt;&lt; endl;
std::cout &lt;&lt;"Unsigned Int Max "&lt;&lt; std::numeric_limits&lt;unsignedint&gt;::max()&lt;&lt; endl;
std::cout &lt;&lt;"Long Int Min "&lt;&lt; std::numeric_limits&lt;longint&gt;::min()&lt;&lt; endl;
std::cout &lt;&lt;"Long Int Max "&lt;&lt; std::numeric_limits&lt;longint&gt;::max()&lt;&lt; endl;
    

    std::cout &lt;&lt;"Unsigned Long Int Min "&lt;&lt; std::numeric_limits&lt;unsignedlongint&gt;::min()&lt;&lt;endl;
std::cout &lt;&lt;"Unsigned Long Int Max "&lt;&lt; std::numeric_limits&lt;unsignedlongint&gt;::max()&lt;&lt; endl;}</code></pre>
    



    typedef Declarations
    




    You can create a new name for an existing type using typedef. Following is the simple syntax to define a new type using typedef −
    




    typedef type newname; 

    




    For example, the following tells the compiler that feet is another name for int −
    




    typedef int feet;

    




    Now, the following declaration is perfectly legal and creates an integer variable called distance −
    




    feet distance;

    




    Enumerated Types
    




    An enumerated type declares an optional type name and a set of zero or more identifiers that can be used as values of the type. Each enumerator is a constant whose type is the enumeration.
    




    Creating an enumeration requires the use of the keyword enum. The general form of an enumeration type is −
    




    enum enum-name { list of names } var-list; 

    




    Here, the enum-name is the enumeration's type name. The list of names is comma separated.
    




    For example, the following code defines an enumeration of colors called colors and the variable c of type color. Finally, c is assigned the value "blue".
    




    enum color { red, green, blue } c;
c = blue;

    




    By default, the value of the first name is 0, the second name has the value 1, and the third has the value 2, and so on. But you can give a name, a specific value by adding an initializer. For example, in the following enumeration, green will have the value 5.
    




    enum color { red, green = 5, blue };

    




    Here, blue will have a value of 6 because each name will be one greater than the one that precedes it.

  • Comments in C++

    Program comments are explanatory statements that you can include in the C++ code. These comments help anyone reading the source code. All programming languages allow for some form of comments.

    C++ supports single-line and multi-line comments. All characters available inside any comment are ignored by C++ compiler.

    C++ comments start with /* and end with */. For example −

    /* This is a comment */

/* C++ comments can also
   * span multiple lines
*/

    A comment can also start with //, extending to the end of the line. For example −

    #include <iostream>
using namespace std;

main() {
   cout << "Hello World"; // prints Hello World
   
   return 0;
}

    When the above code is compiled, it will ignore // prints Hello World and final executable will produce the following result −

    Hello World

    Within a /* and */ comment, // characters have no special meaning. Within a // comment, /* and */ have no special meaning. Thus, you can “nest” one kind of comment within the other kind. For example −

    /* Comment out printing of Hello World:

cout << "Hello World"; // prints Hello World

*/

  • C++ Basic Syntax

    When we consider a C++ program, it can be defined as a collection of objects that communicate via invoking each other’s methods. Let us now briefly look into what a class, object, methods, and instant variables mean.

    • Object − Objects have states and behaviors. Example: A dog has states – color, name, breed as well as behaviors – wagging, barking, eating. An object is an instance of a class.
    • Class − A class can be defined as a template/blueprint that describes the behaviors/states that object of its type support.
    • Methods − A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed.
    • Instance Variables − Each object has its unique set of instance variables. An object’s state is created by the values assigned to these instance variables.

    C++ Program Structure

    Let us look at a simple code that would print the words Hello World.

    #include <iostream>
using namespace std;

// main() is where program execution begins.
int main() {
   cout << "Hello World"; // prints Hello World
   return 0;
}

    Let us look at the various parts of the above program −

    • The C++ language defines several headers, which contain information that is either necessary or useful to your program. For this program, the header <iostream> is needed.
    • The line using namespace std; tells the compiler to use the std namespace. Namespaces are a relatively recent addition to C++.
    • The next line ‘// main() is where program execution begins.‘ is a single-line comment available in C++. Single-line comments begin with // and stop at the end of the line.
    • The line int main() is the main function where program execution begins.
    • The next line cout << “Hello World”; causes the message “Hello World” to be displayed on the screen.
    • The next line return 0; terminates main( )function and causes it to return the value 0 to the calling process.

    Compile and Execute C++ Program

    Let’s look at how to save the file, compile and run the program. Please follow the steps given below −

    • Open a text editor and add the code as above.
    • Save the file as: hello.cpp
    • Open a command prompt and go to the directory where you saved the file.
    • Type ‘g++ hello.cpp’ and press enter to compile your code. If there are no errors in your code the command prompt will take you to the next line and would generate a.out executable file.
    • Now, type ‘a.out’ to run your program.
    • You will be able to see ‘ Hello World ‘ printed on the window.
    $ g++ hello.cpp
$ ./a.out
Hello World

    Make sure that g++ is in your path and that you are running it in the directory containing file hello.cpp.

    You can compile C/C++ programs using makefile. For more details, you can check our ‘Makefile Tutorial’.

    Semicolons and Blocks in C++

    In C++, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.

    For example, following are three different statements −

    x = y;
y = y + 1;
add(x, y);

    A block is a set of logically connected statements that are surrounded by opening and closing braces. For example −

    {
   cout << "Hello World"; // prints Hello World
   return 0;
}

    C++ does not recognize the end of the line as a terminator. For this reason, it does not matter where you put a statement in a line. For example −

    x = y;
y = y + 1;
add(x, y);

    is the same as

    x = y; y = y + 1; add(x, y);

    C++ Identifiers

    A C++ identifier is a name used to identify a variable, function, class, module, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores, and digits (0 to 9).

    C++ does not allow punctuation characters such as @, $, and % within identifiers. C++ is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in C++.

    Here are some examples of acceptable identifiers −

    mohd       zara    abc   move_name  a_123
myname50   _temp   j     a23b9      retVal

    C++ Keywords

    The following list shows the reserved words in C++. These reserved words may not be used as constant or variable or any other identifier names.

    asmelsenewthis
    autoenumoperatorthrow
    boolexplicitprivatetrue
    breakexportprotectedtry
    caseexternpublictypedef
    catchfalseregistertypeid
    charfloatreinterpret_casttypename
    classforreturnunion
    constfriendshortunsigned
    const_castgotosignedusing
    continueifsizeofvirtual
    defaultinlinestaticvoid
    deleteintstatic_castvolatile
    dolongstructwchar_t
    doublemutableswitchwhile
    dynamic_castnamespacetemplate 

    Trigraphs

    A few characters have an alternative representation, called a trigraph sequence. A trigraph is a three-character sequence that represents a single character and the sequence always starts with two question marks.

    Trigraphs are expanded anywhere they appear, including within string literals and character literals, in comments, and in preprocessor directives.

    Following are most frequently used trigraph sequences −

    TrigraphReplacement
    ??=#
    ??/\
    ??’^
    ??([
    ??)]
    ??!|
    ??<{
    ??>}
    ??-~

    All the compilers do not support trigraphs and they are not advised to be used because of their confusing nature.

    Whitespace in C++

    A line containing only whitespace, possibly with a comment, is known as a blank line, and C++ compiler totally ignores it.

    Whitespace is the term used in C++ to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins.

    Statement 1

    int age;

    In the above statement there must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them.

    Statement 2

    fruit = apples + oranges;   // Get the total fruit

    In the above statement 2, no whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.

  • C++ Environment Setup

    Local Environment Setup

    If you are still willing to set up your environment for C++, you need to have the following two softwares on your computer.

    Text Editor

    This will be used to type your program. Examples of few editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi.

    Name and version of text editor can vary on different operating systems. For example, Notepad will be used on Windows and vim or vi can be used on windows as well as Linux, or UNIX.

    The files you create with your editor are called source files and for C++ they typically are named with the extension .cpp, .cp, or .c.

    A text editor should be in place to start your C++ programming.

    C++ Compiler

    This is an actual C++ compiler, which will be used to compile your source code into final executable program.

    Most C++ compilers don’t care what extension you give to your source code, but if you don’t specify otherwise, many will use .cpp by default.

    Most frequently used and free available compiler is GNU C/C++ compiler, otherwise you can have compilers either from HP or Solaris if you have the respective Operating Systems.

    Installing GNU C/C++ Compiler

    UNIX/Linux Installation

    If you are using Linux or UNIX then check whether GCC is installed on your system by entering the following command from the command line −

    $ g++ -v

    If you have installed GCC, then it should print a message such as the following −

    Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr .......
Thread model: posix
gcc version 4.1.2 20080704 (Red Hat 4.1.2-46)

    If GCC is not installed, then you will have to install it yourself using the detailed instructions available at https://gcc.gnu.org/install/

    Mac OS X Installation

    If you use Mac OS X, the easiest way to obtain GCC is to download the Xcode development environment from Apple’s website and follow the simple installation instructions.

    Xcode is currently available at developer.apple.com/technologies/tools/.

    Windows Installation

    To install GCC at Windows you need to install MinGW. To install MinGW, go to the MinGW homepage, www.mingw.org, and follow the link to the MinGW download page. Download the latest version of the MinGW installation program which should be named MinGW-<version>.exe.

    While installing MinGW, at a minimum, you must install gcc-core, gcc-g++, binutils, and the MinGW runtime, but you may wish to install more.

    Add the bin subdirectory of your MinGW installation to your PATH environment variable so that you can specify these tools on the command line by their simple names.

    When the installation is complete, you will be able to run gcc, g++, ar, ranlib, dlltool, and several other GNU tools from the Windows command line.

  • Overview

    C++ is a statically typed, compiled, general-purpose, case-sensitive, free-form programming language that supports procedural, object-oriented, and generic programming.

    C++ is regarded as a middle-level language, as it comprises a combination of both high-level and low-level language features.

    C++ was developed by Bjarne Stroustrup starting in 1979 at Bell Labs in Murray Hill, New Jersey, as an enhancement to the C language and originally named C with Classes but later it was renamed C++ in 1983.

    C++ is a superset of C, and that virtually any legal C program is a legal C++ program.

    Note − A programming language is said to use static typing when type checking is performed during compile-time as opposed to run-time.

    Object-Oriented Programming

    C++ fully supports object-oriented programming, including the four pillars of object-oriented development −

    • Encapsulation
    • Data hiding
    • Inheritance
    • Polymorphism

    Standard Libraries

    Standard C++ consists of three important parts −

    • The core language giving all the building blocks including variables, data types and literals, etc.
    • The C++ Standard Library giving a rich set of functions manipulating files, strings, etc.
    • The Standard Template Library (STL) giving a rich set of methods manipulating data structures, etc.

    The ANSI Standard

    The ANSI standard is an attempt to ensure that C++ is portable; that code you write for Microsoft’s compiler will compile without errors, using a compiler on a Mac, UNIX, a Windows box, or an Alpha.

    The ANSI standard has been stable for a while, and all the major C++ compiler manufacturers support the ANSI standard.

    Learning C++

    The most important thing while learning C++ is to focus on concepts.

    The purpose of learning a programming language is to become a better programmer; that is, to become more effective at designing and implementing new systems and at maintaining old ones.

    C++ supports a variety of programming styles. You can write in the style of Fortran, C, Smalltalk, etc., in any language. Each style can achieve its aims effectively while maintaining runtime and space efficiency.

    Use of C++

    C++ is used by hundreds of thousands of programmers in essentially every application domain.

    C++ is being highly used to write device drivers and other software that rely on direct manipulation of hardware under realtime constraints.

    C++ is widely used for teaching and research because it is clean enough for successful teaching of basic concepts.

    Anyone who has used either an Apple Macintosh or a PC running Windows has indirectly used C++ because the primary user interfaces of these systems are written in C++.

  • String Handling

    String handling statements in COBOL are used to do multiple functional operations on strings. Following are the string handling statements −

    • Inspect
    • String
    • Unstring

    Inspect

    Inspect verb is used to count or replace the characters in a string. String operations can be performed on alphanumeric, numeric, or alphabetic values. Inspect operations are performed from left to right. The options used for the string operations are as follows −

    Tallying

    Tallying option is used to count the string characters.

    Syntax

    Following is the syntax of Tallying option −

    INSPECT input-string
TALLYING output-count FOR ALL CHARACTERS

    The parameters used are −

    • input-string − The string whose characters are to be counted.
    • output-count − Data item to hold the count of characters.

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-CNT1 PIC 9(2) VALUE 0.
   01 WS-CNT2 PIC 9(2) VALUE 0.
   01 WS-STRING PIC X(15) VALUE 'ABCDACDADEAAAFF'.
   
PROCEDURE DIVISION.
   INSPECT WS-STRING TALLYING WS-CNT1 FOR CHARACTER.
   DISPLAY "WS-CNT1 : "WS-CNT1.
   INSPECT WS-STRING TALLYING WS-CNT2 FOR ALL 'A'.
   DISPLAY "WS-CNT2 : "WS-CNT2
   
STOP RUN.

    JCL to execute the above COBOL program.

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-CNT1 : 15
WS-CNT2 : 06

    Replacing

    Replacing option is used to replace the string characters.

    Syntax

    Following is the syntax of Replacing option −

    INSPECT input-string REPLACING ALL char1 BY char2.

    The parameter used is −

    • input-string − The string whose characters are to be replaced from char1 to char2.

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-STRING PIC X(15) VALUE 'ABCDACDADEAAAFF'.

PROCEDURE DIVISION.
   DISPLAY "OLD STRING : "WS-STRING.
   INSPECT WS-STRING REPLACING ALL 'A' BY 'X'.
   DISPLAY "NEW STRING : "WS-STRING.
   
STOP RUN.

    JCL to execute the above COBOL program.

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    OLD STRING : ABCDACDADEAAAFF
NEW STRING : XBCDXCDXDEXXXFF

    String

    String verb is used to concatenate the strings. Using STRING statement, two or more strings of characters can be combined to form a longer string. ‘Delimited By’ clause is compulsory.

    Syntax

    Following is the syntax of String verb −

    STRING ws-string1 DELIMITED BY SPACE
   ws-string2 DELIMITED BY SIZE
   INTO ws-destination-string
   WITH POINTER ws-count
   ON OVERFLOW DISPLAY message1
   NOT ON OVERFLOW DISPLAY message2
END-STRING.

    Following are the details of the used parameters −

    • ws-string1 and ws-string2 : Input strings to be concatenated
    • ws-string : Output string
    • ws-count : Used to count the length of new concatenated string
    • Delimited specifies the end of string
    • Pointer and Overflow are optional

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-STRING PIC A(30).
   01 WS-STR1 PIC A(15) VALUE 'Tutorialspoint'.
   01 WS-STR2 PIC A(7) VALUE 'Welcome'.
   01 WS-STR3 PIC A(7) VALUE 'To AND'.
   01 WS-COUNT PIC 99 VALUE 1.

PROCEDURE DIVISION.
   STRING WS-STR2 DELIMITED BY SIZE

      WS-STR3 DELIMITED BY SPACE
  WS-STR1 DELIMITED BY SIZE
  INTO WS-STRING 
  WITH POINTER WS-COUNT
  ON OVERFLOW DISPLAY 'OVERFLOW!' 
       END-STRING.
   
   DISPLAY 'WS-STRING : 'WS-STRING.
   DISPLAY 'WS-COUNT : 'WS-COUNT.

STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-STRING : WelcomeToTutorialspoint       
WS-COUNT : 25

    Unstring

    Unstring verb is used to split one string into multiple sub-strings. Delimited By clause is compulsory.

    Syntax

    Following is the syntax of Unstring verb −

    UNSTRING ws-string DELIMITED BY SPACE
INTO ws-str1, ws-str2
WITH POINTER ws-count
ON OVERFLOW DISPLAY message
NOT ON OVERFLOW DISPLAY message
END-UNSTRING.

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-STRING PIC A(30) VALUE 'WELCOME TO TUTORIALSPOINT'.
   01 WS-STR1 PIC A(7).
   01 WS-STR2 PIC A(2).
   01 WS-STR3 PIC A(15).
   01 WS-COUNT PIC 99 VALUE 1.

PROCEDURE DIVISION.
   UNSTRING WS-STRING DELIMITED BY SPACE

      INTO WS-STR1, WS-STR2, WS-STR3
       END-UNSTRING.
   
   DISPLAY 'WS-STR1 : 'WS-STR1.
   DISPLAY 'WS-STR2 : 'WS-STR2.
   DISPLAY 'WS-STR3 : 'WS-STR3.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-STR1 : WELCOME
WS-STR2 : TO
WS-STR3 : TUTORIALSPOINT

  • Loop Statements

    There are some tasks that need to be done over and over again like reading each record of a file till its end. The loop statements used in COBOL are −

    • Perform Thru
    • Perform Until
    • Perform Times
    • Perform Varying

    Perform Thru

    Perform Thru is used to execute a series of paragraph by giving the first and last paragraph names in the sequence. After executing the last paragraph, the control is returned back.

    In-line Perform

    Statements inside the PERFORM will be executed till END-PERFORM is reached.

    Syntax

    Following is the syntax of In-line perform −

    PERFORM 
   DISPLAY 'HELLO WORLD'
END-PERFORM.

    Out-of-line Perform

    Here, a statement is executed in one paragraph and then the control is transferred to other paragraph or section.

    Syntax

    Following is the syntax of Out-of-line perform −

    PERFORM PARAGRAPH1 THRU PARAGRAPH2

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

PROCEDURE DIVISION.
   A-PARA.
   PERFORM DISPLAY 'IN A-PARA'
   END-PERFORM.
   PERFORM C-PARA THRU E-PARA.
   
   B-PARA.
   DISPLAY 'IN B-PARA'.
   STOP RUN.
   
   C-PARA.
   DISPLAY 'IN C-PARA'.
   
   D-PARA.
   DISPLAY 'IN D-PARA'.
   
   E-PARA.
   DISPLAY 'IN E-PARA'.

    JCL to execute the above COBOL program.

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    IN A-PARA
IN C-PARA
IN D-PARA
IN E-PARA
IN B-PARA

    Perform Until

    In ‘perform until’, a paragraph is executed until the given condition becomes true. ‘With test before’ is the default condition and it indicates that the condition is checked before the execution of statements in a paragraph.

    Syntax

    Following is the syntax of perform until −

    PERFORM A-PARA UNTIL COUNT=5

PERFORM A-PARA WITH TEST BEFORE UNTIL COUNT=5

PERFORM A-PARA WITH TEST AFTER UNTIL COUNT=5

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-CNT PIC 9(1) VALUE 0. 

PROCEDURE DIVISION.
   A-PARA.
   PERFORM B-PARA WITH TEST AFTER UNTIL WS-CNT>3.
   STOP RUN.
   
   B-PARA.
   DISPLAY 'WS-CNT : 'WS-CNT.
   ADD 1 TO WS-CNT.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-CNT : 0
WS-CNT : 1
WS-CNT : 2
WS-CNT : 3

    Perform Times

    In ‘perform times’, a paragraph will be executed the number of times specified.

    Syntax

    Following is the syntax of perform times −

    PERFORM A-PARA 5 TIMES.

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

PROCEDURE DIVISION.
   A-PARA.
   PERFORM B-PARA 3 TIMES.
   STOP RUN.
   
   B-PARA.
   DISPLAY 'IN B-PARA'.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    IN B-PARA
IN B-PARA
IN B-PARA

    Perform Varying

    In perform varying, a paragraph will be executed till the condition in Until phrase becomes true.

    Syntax

    Following is the syntax of perform varying −

    PERFORM A-PARA VARYING A FROM 1 BY 1 UNTIL A = 5.

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-A PIC 9 VALUE 0.

PROCEDURE DIVISION.
   A-PARA.
   PERFORM B-PARA VARYING WS-A FROM 1 BY 1 UNTIL WS-A=5
   STOP RUN.
   
   B-PARA.
   DISPLAY 'IN B-PARA ' WS-A.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    IN B-PARA 1
IN B-PARA 2
IN B-PARA 3
IN B-PARA 4

    GO TO Statement

    GO TO statement is used to change the flow of execution in a program. In GO TO statements, transfer goes only in the forward direction. It is used to exit a paragraph. The different types of GO TO statements used are as follows −

    Unconditional GO TO

    GO TO para-name.

    Conditional GO TO

    GO TO para-1 para-2 para-3 DEPENDING ON x.

    If ‘x’ is equal to 1, then the control will be transferred to the first paragraph; and if ‘x’ is equal to 2, then the control will be transferred to the second paragraph, and so on.

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-A PIC 9 VALUE 2.
   
PROCEDURE DIVISION.
   A-PARA.
   DISPLAY 'IN A-PARA'
   GO TO B-PARA.
   
   B-PARA.
   DISPLAY 'IN B-PARA '.
   GO TO C-PARA D-PARA DEPENDING ON WS-A.
   
   C-PARA.
   DISPLAY 'IN C-PARA '.
   
   D-PARA.
   DISPLAY 'IN D-PARA '.
   STOP RUN.

    JCL to execute the above COBOL program:

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result:

    IN A-PARA
IN B-PARA 
IN D-PARA

  • Conditional Statements

    Conditional statements are used to change the execution flow depending on certain conditions specified by the programmer. Conditional statements will always evaluate to true or false. Conditions are used in IF, Evaluate, and Perform statements. The different types of conditions are as follows −

    • IF Condition Statement
    • Relation Condition
    • Sign Condition
    • Class Condition
    • Condition-Name Condition
    • Negated Condition
    • Combined Condition

    IF Condition Statement

    IF statement checks for conditions. If a condition is true, the IF block is executed; and if the condition is false, the ELSE block is executed.

    END-IF is used to end the IF block. To end the IF block, a period can be used instead of END-IF. But it is always preferable to use END-IF for multiple IF blocks.

    Nested-IF − IF blocks appearing inside another IF block. There is no limit to the depth of nested IF statements.

    Syntax

    Following is the syntax of IF condition statements −

    IF [condition] THEN
   [COBOL statements]
ELSE
   [COBOL statements]
END-IF.

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(9).
   01 WS-NUM2 PIC 9(9).
   01 WS-NUM3 PIC 9(5).
   01 WS-NUM4 PIC 9(6).

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 25 TO WS-NUM1 WS-NUM3.
   MOVE 15 TO WS-NUM2 WS-NUM4.
   
   IF WS-NUM1 > WS-NUM2 THEN

      DISPLAY 'IN LOOP 1 - IF BLOCK'
  
  IF WS-NUM3 = WS-NUM4 THEN
     DISPLAY 'IN LOOP 2 - IF BLOCK'
  ELSE
     DISPLAY 'IN LOOP 2 - ELSE BLOCK'
  END-IF
  
       ELSE

      DISPLAY 'IN LOOP 1 - ELSE BLOCK'
       END-IF.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    IN LOOP 1 - IF BLOCK
IN LOOP 2 - ELSE BLOCK

    Relation Condition

    Relation condition compares two operands, either of which can be an identifier, literal, or arithmetic expression. Algebraic comparison of numeric fields is done regardless of size and usage clause.

    For non-numeric operands

    If two non-numeric operands of equal size are compared, then the characters are compared from left with the corresponding positions till the end is reached. The operand containing greater number of characters is declared greater.

    If two non-numeric operands of unequal size are compared, then the shorter data item is appended with spaces at the end till the size of the operands becomes equal and then compared according to the rules mentioned in the previous point.

    Syntax

    Given below is the syntax of Relation condition statements −

    [Data Name/Arithmetic Operation]

   [IS] [NOT] 

[Equal to (=),Greater than (>), Less than (<), 
Greater than or Equal (>=), Less than or equal (<=) ]

[Data Name/Arithmetic Operation]

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(9).
   01 WS-NUM2 PIC 9(9).

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 25 TO WS-NUM1.
   MOVE 15 TO WS-NUM2.
   
   IF WS-NUM1 IS GREATER THAN OR EQUAL TO WS-NUM2 THEN

      DISPLAY 'WS-NUM1 IS GREATER THAN WS-NUM2'
       ELSE

      DISPLAY 'WS-NUM1 IS LESS THAN WS-NUM2'
       END-IF.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program it produces the following result −

    WS-NUM1 IS GREATER THAN WS-NUM2

    Sign Condition

    Sign condition is used to check the sign of a numeric operand. It determines whether a given numeric value is greater than, less than, or equal to ZERO.

    Syntax

    Following is the syntax of Sign condition statements −

    [Data Name/Arithmetic Operation] 

   [IS] [NOT] 

[Positive, Negative or Zero]

[Data Name/Arithmetic Operation]

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC S9(9) VALUE -1234.
   01 WS-NUM2 PIC S9(9) VALUE 123456.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   IF WS-NUM1 IS POSITIVE THEN

      DISPLAY 'WS-NUM1 IS POSITIVE'.
  
       IF WS-NUM1 IS NEGATIVE THEN

      DISPLAY 'WS-NUM1 IS NEGATIVE'.
  
       IF WS-NUM1 IS ZERO THEN

      DISPLAY 'WS-NUM1 IS ZERO'.
  
       IF WS-NUM2 IS POSITIVE THEN

      DISPLAY 'WS-NUM2 IS POSITIVE'.
    
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program it produces the following result −

    WS-NUM1 IS NEGATIVE
WS-NUM2 IS POSITIVE

    Class Condition

    Class condition is used to check if an operand contains only alphabets or numeric data. Spaces are considered in ALPHABETIC, ALPHABETIC-LOWER, and ALPHABETIC-UPPER.

    Syntax

    Following is the syntax of Class condition statements −

    [Data Name/Arithmetic Operation>]

   [IS] [NOT] 

[NUMERIC, ALPHABETIC, ALPHABETIC-LOWER, ALPHABETIC-UPPER]

[Data Name/Arithmetic Operation]

    Example

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC X(9) VALUE 'ABCD '.
   01 WS-NUM2 PIC 9(9) VALUE 123456789.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF WS-NUM1 IS ALPHABETIC THEN

      DISPLAY 'WS-NUM1 IS ALPHABETIC'.
  
       IF WS-NUM1 IS NUMERIC THEN

      DISPLAY 'WS-NUM1 IS NUMERIC'.
  
       IF WS-NUM2 IS NUMERIC THEN

      DISPLAY 'WS-NUM2 IS NUMERIC'.
       
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-NUM1 IS ALPHABETIC
WS-NUM2 IS NUMERIC

    Condition-name Condition

    A condition-name is a user-defined name. It contains a set of values specified by the user. It behaves like Boolean variables. They are defined with level number 88. It will not have a PIC clause.

    Syntax

    Following is the syntax of user-defined condition statements −

    88 [Condition-Name] VALUE [IS, ARE] [LITERAL] [THRU LITERAL].

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM PIC 9(3).
   88 PASS VALUES ARE 041 THRU 100.
   88 FAIL VALUES ARE 000 THRU 40.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   MOVE 65 TO WS-NUM.
   
   IF PASS 

      DISPLAY 'Passed with ' WS-NUM ' marks'.
  
       IF FAIL 

      DISPLAY 'FAILED with ' WS-NUM 'marks'.
  
    STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    Passed with 065 marks

    Negated Condition

    Negated condition is given by using the NOT keyword. If a condition is true and we have given NOT in front of it, then its final value will be false.

    Syntax

    Following is the syntax of Negated condition statements −

    IF NOT [CONDITION] 
   COBOL Statements
END-IF.

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(2) VALUE 20.
   01 WS-NUM2 PIC 9(9) VALUE 25.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF NOT WS-NUM1 IS LESS THAN WS-NUM2 THEN

      DISPLAY 'IF-BLOCK'
       ELSE

      DISPLAY 'ELSE-BLOCK'
       END-IF.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    ELSE-BLOCK

    Combined Condition

    A combined condition contains two or more conditions connected using logical operators AND or OR.

    Syntax

    Following is the syntax of combined condition statements −

    IF [CONDITION] AND [CONDITION]
   COBOL Statements
END-IF.

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-NUM1 PIC 9(2) VALUE 20.
   01 WS-NUM2 PIC 9(2) VALUE 25.
   01 WS-NUM3 PIC 9(2) VALUE 20.

PROCEDURE DIVISION.
   A000-FIRST-PARA.
   
   IF WS-NUM1 IS LESS THAN WS-NUM2 AND WS-NUM1=WS-NUM3 THEN

      DISPLAY 'Both condition OK'
       ELSE

      DISPLAY 'Error'
       END-IF.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    Both condition OK

    Evaluate Verb

    Evaluate verb is a replacement of series of IF-ELSE statement. It can be used to evaluate more than one condition. It is similar to SWITCH statement in C programs.

    Example

    Live Demo

    IDENTIFICATION DIVISION.
PROGRAM-ID. HELLO.

DATA DIVISION.
   WORKING-STORAGE SECTION.
   01 WS-A PIC 9 VALUE 0.
   
PROCEDURE DIVISION.
   MOVE 3 TO WS-A.
   
   EVALUATE TRUE

      WHEN WS-A &gt; 2
     DISPLAY 'WS-A GREATER THAN 2'
    

      WHEN WS-A &lt; 0
     DISPLAY 'WS-A LESS THAN 0'
    

      WHEN OTHER
     DISPLAY 'INVALID VALUE OF WS-A'
       END-EVALUATE.
   
STOP RUN.

    JCL to execute the above COBOL program −

    //SAMPLE JOB(TESTJCL,XXXXXX),CLASS = A,MSGCLASS = C
//STEP1 EXEC PGM = HELLO

    When you compile and execute the above program, it produces the following result −

    WS-A GREATER THAN 2