Explain syntax and semantics of "for loop " n "while loop" in c language
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FOR - for loops are the most useful type. The syntax for a for loop is
for ( variable initialization; condition; variable update ) {
Code to execute while the condition is true
}
The variable initialization allows you to either declare a variable and give it a value or give a value to an already existing variable. Second, the condition tells the program that while the conditional expression is true the loop should continue to repeat itself. The variable update section is the easiest way for a for loop to handle changing of the variable. It is possible to do things like x++, x = x + 10, or even x = random ( 5 ), and if you really wanted to, you could call other functions that do nothing to the variable but still have a useful effect on the code. Notice that a semicolon separates each of these sections, that is important. Also note that every single one of the sections may be empty, though the semicolons still have to be there. If the condition is empty, it is evaluated as true and the loop will repeat until something else stops it.
Example:
#include <stdio.h>
int main()
{
int x;
/* The loop goes while x < 10, and x increases by one every loop*/
for ( x = 0; x < 10; x++ ) {
/* Keep in mind that the loop condition checks
the conditional statement before it loops again.
consequently, when x equals 10 the loop breaks.
x is updated before the condition is checked. */
printf( "%d\n", x );
}
getchar();
}
This program is a very simple example of a for loop. x is set to zero, while x is less than 10 it calls printf to display the value of the variable x, and it adds 1 to x until the condition is met. Keep in mind also that the variable is incremented after the code in the loop is run for the first time.
WHILE - WHILE loops are very simple. The basic structure is
while ( condition ) { Code to execute while the condition is true } The true represents a boolean expression which could be x == 1 or while ( x != 7 ) (x does not equal 7). It can be any combination of boolean statements that are legal. Even, (while x ==5 || v == 7) which says execute the code while x equals five or while v equals 7. Notice that a while loop is like a stripped-down version of a for loop-- it has no initialization or update section. However, an empty condition is not legal for a while loop as it is with a for loop.
Example:
#include <stdio.h>
int main()
{
int x = 0; /* Don't forget to declare variables */
while ( x < 10 ) { /* While x is less than 10 */
printf( "%d\n", x );
x++; /* Update x so the condition can be met eventually */
}
getchar();
}
This was another simple example, but it is longer than the above FOR loop. The easiest way to think of the loop is that when it reaches the brace at the end it jumps back up to the beginning of the loop, which checks the condition again and decides whether to repeat the block another time, or stop and move to the next statement after the block.
for ( variable initialization; condition; variable update ) {
Code to execute while the condition is true
}
The variable initialization allows you to either declare a variable and give it a value or give a value to an already existing variable. Second, the condition tells the program that while the conditional expression is true the loop should continue to repeat itself. The variable update section is the easiest way for a for loop to handle changing of the variable. It is possible to do things like x++, x = x + 10, or even x = random ( 5 ), and if you really wanted to, you could call other functions that do nothing to the variable but still have a useful effect on the code. Notice that a semicolon separates each of these sections, that is important. Also note that every single one of the sections may be empty, though the semicolons still have to be there. If the condition is empty, it is evaluated as true and the loop will repeat until something else stops it.
Example:
#include <stdio.h>
int main()
{
int x;
/* The loop goes while x < 10, and x increases by one every loop*/
for ( x = 0; x < 10; x++ ) {
/* Keep in mind that the loop condition checks
the conditional statement before it loops again.
consequently, when x equals 10 the loop breaks.
x is updated before the condition is checked. */
printf( "%d\n", x );
}
getchar();
}
This program is a very simple example of a for loop. x is set to zero, while x is less than 10 it calls printf to display the value of the variable x, and it adds 1 to x until the condition is met. Keep in mind also that the variable is incremented after the code in the loop is run for the first time.
WHILE - WHILE loops are very simple. The basic structure is
while ( condition ) { Code to execute while the condition is true } The true represents a boolean expression which could be x == 1 or while ( x != 7 ) (x does not equal 7). It can be any combination of boolean statements that are legal. Even, (while x ==5 || v == 7) which says execute the code while x equals five or while v equals 7. Notice that a while loop is like a stripped-down version of a for loop-- it has no initialization or update section. However, an empty condition is not legal for a while loop as it is with a for loop.
Example:
#include <stdio.h>
int main()
{
int x = 0; /* Don't forget to declare variables */
while ( x < 10 ) { /* While x is less than 10 */
printf( "%d\n", x );
x++; /* Update x so the condition can be met eventually */
}
getchar();
}
This was another simple example, but it is longer than the above FOR loop. The easiest way to think of the loop is that when it reaches the brace at the end it jumps back up to the beginning of the loop, which checks the condition again and decides whether to repeat the block another time, or stop and move to the next statement after the block.
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