What is for Loop in C and C++ Language
The for Loop
The general design of the for loop is reflected in some form or another in all procedural programming languages. However, in C/C++, it provides unexpected flexibility and power. The general form of the for statement is for (initialization; condition; increment) statement; the for loop allows many variations, but its most common form works like this. The initialization is an assignment statement that is used to set the loop control variable. The condition is a relational expression that determines when the loop exits. The increment defines how the loop control variable changes each time the loop is repeated. You must separate these three major sections by semicolons. The for loop continues to execute as long as the condition is true. Once the condition becomes false, program execution resumes on the statement following the for.
In the following program, a for loop is used to print the numbers 1 through 100 on the screen:
#include
int main(void)
{
int x;
for(x=1; x <= 100; x++) printf(”%d “, x);
return 0;
}
In the loop, x is initially set to 1 and then compared with 100. Since x is less than 100, printf() is called and the loop iterates. This causes x to be increased by 1 and again tested to see if it is still less than or equal to 100. If it is, printf() is called. This process repeats until x is greater than 100, at which point the loop terminates. In this example, x is the loop control variable, which is changed and checked each time the loop repeats. The following example is a for loop that iterates multiple statements:
for(x=100; x != 65; x -= 5) {
z = x*x;
printf(”The square of %d, %f”, x, z);
}
Both the squaring of x and the call to printf() are executed until x equals 65. Note that the loop is negative running: x is initialized to 100 and 5 is subtracted from it each time the loop repeats. In for loops, the conditional test is always performed at the top of the loop. This means that the code inside the loop may not be executed at all if the condition is false to begin with. For example, in
x = 10;
for(y=10; y!=x; ++y) printf(”%d”, y);
printf(”%d”, y); /* this is the only printf()
statement that will execute */
The loop will never execute because x and y are equal when the loop is entered. Because this causes the conditional expression to evaluate to false, neither the body of the loop nor the increment portion of the loop executes. Hence, y still has the value 10, and the only output produced by the fragment is the number 10 printed once on the screen.
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