Loop For, While and Do-While in C Language

All loops have the same function, which is to repeat an instruction a certain or undetermined number of times.

The structure of the FOR loop is as follows:

for(inicialização; condição; incremento)
comandos;

For example:

#include

voi main()
{
int x;

for(x = 0; x <= 100; x++) printf("%d", x); } 

The program above displays numbers from 0 to 100 on the screen. The FOR loop is usually also used to make infinite loops since its fields are not mandatory, but this is just a custom, which does not prevent you from using the WHILE loop instead of FOR.

Example of an infinite loop with FOR:

#include

void main()
{
int x;
for(x = 0; ; x++)
printf("%d", x);
}

Structure of the While loop:

while(condição)
comando;

Example:

include

void main()
{
int x;
while(x != 0)
{
printf("Insira um valor para X: ");
scanf("%d", x);
}
}

The WHILE loop is repeated until the user enters the value zero.

Structure of the Do-While loop:

do{
comando1;
comando2;
}
while(condição);

The Do-While loop, unlike the FOR and WHILE loops, tests the condition at the end of execution, i.e. the commands inside the ‘Do’ keys:

do{
command1;
command2;
}

are executed, then the condition inside the WHILE is tested, if true the commands inside the ‘Do’ braces are executed again, if false the program exits the loop.