goto statement

The Goto statement :-


C language supports "goto" statement to branch unconditionally from one point to another in the program.
The goto requires a label in order to identify the place where the branch is to be made. A label is any valid variable name, and must be followed by a colon. The label is placed just before the statement where the control is to be transferred. 

The general forms of goto and label statements are:-














The "label:" can be anywhere in the program either before or after the "goto label;" statement.
While executing the program,when a statement like "goto begin;" is met, the flow of control will jump to the statement immediately following the label "begin:". A goto breaks the normal sequencial execution of the program. If the "label:" is before the statement "goto label;"  a loop will be formed and some statments will be executed repeatedly. Such a jump is called backward jump. And, if the "label:" is placed after the"goto label;", some statements will be skipped and the jump is knwn as forward jump. "goto" statement is usually used at the end of a program to direct the control to go to  the input statement, to read further data. Consider an example :-
main()
{
       int  x,y;   
       read:
       scanf("%d", &x);
       if (x<0) goto read;
       y = sqrt(x);
       printf("%d  %d\n", x,y);
       goto read;
}
This program is written to evaluate the square root of a series of numbers read from the terminal. The program uses two goto statements, one at the end, after printing the results to transfer the control back to the input statement and the other is to skip any further computation when the number is negative. Due to unconditional goto statement at the end, the control is always transferred back to the input statement. When the program puts the comuter in a permanent loop, such situation is called as an "infinite loop". In such situation, computer goes round and round until we takes some special steps to terminate the loop. Another use of goto statement is to transfer the control out of a loop when certain pecular conditions are encountered. We should try to avoid using goto as much as possible. But there is nothing wrong, if we use it to enhance the readability of the program or to improve the execution speed.                                                                                                                                                                                                                                                                                                                                                              


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