For, Continue

For Loop

The for loop incorporates the counter's initialization, the condition to exit the loop, and the counter's update.


python
9
1
2
3
4
for (initialization; condition; update)
{
	// loop body
}

Let's take the example from the previous lesson (displaying array elements) and reframe it using a for loop:

Main

#include <stdio.h>

int main()

{

int array[] = { 3, 6, 2, 134, 45,

2, 564, 8, 3, 531 };

for (int i = 0; i < 10; i++)

{

printf("Index of element: %d\tValue of element: %d\n", i, array[i]);

}

return 0;

}


              1234567891011121314
            
#include <stdio.h>

int main()
{
	int array[] = { 3, 6, 2, 134, 45,
				   2, 564, 8, 3, 531 };

	for (int i = 0; i < 10; i++)
	{
		printf("Index of element: %d\tValue of element: %d\n", i, array[i]);
	}

	return 0;
}

Loop's Flexibility

You can use any valid expression as the update counter. This means the counter can adapt based on any valid rule, such as (++x * 3) - 5.

Furthermore, the counter can increment by characters instead of numbers.

Main

#include <stdio.h>

int main()

{

for (char ch = 'a'; ch <= 'z'; ch++)

{

printf("ASCII value for %c is %d\n", ch, ch);

}

return 0;

}


              12345678910
            
#include <stdio.h> 

int main()
{
	for (char ch = 'a'; ch <= 'z'; ch++)
	{
		printf("ASCII value for %c is %d\n", ch, ch);
	}
	return 0;
}

Note

Keep in mind that characters are stored as numbers in memory.

Even if you leave out parts of the loop, like the counter initialization, the program will still compile. However, the semicolon ; remains essential:

Main

#include <stdio.h>

int main()

{

int i = 0;

// without counter initialization

for (printf("It`s count initialization, but printf...\n"); i <= 4; i++)

{

printf("i = %d\n", i);

}

return 0;

}


              12345678910111213
            
#include <stdio.h> 

int main()
{
	int i = 0;
	// without counter initialization
	for (printf("It`s count initialization, but printf...\n"); i <= 4; i++)
	{
		printf("i = %d\n", i);
	}

	return 0;
}

You can use the comma , to separate parts within the loop:

Main

#include <stdio.h>

int main()

{

int i;

int n;

for (i = 0, n = 5; i <= 5; i++, n++)

{

printf("i = %d\t n = %d\n", i, n);

}

return 0;

}


              1234567891011121314
            
#include <stdio.h> 

int main()
{
	int i;
	int n;

	for (i = 0, n = 5; i <= 5; i++, n++)
	{
		printf("i = %d\t n = %d\n", i, n);
	}

return 0;
}

Continue

In loops, both the break and continue commands come in handy. While the break statement forces an exit from the loop, the continue command prompts a skip to the subsequent iteration.

Consider a program designed to exclude negative integers, utilizing the continue operator:

Main

#include <stdio.h>

int main()

{

int array[] = { 124, 235, -321, 32, 54,

-549, 23445, 5534, -433 };

printf("Positive elements of array:\n");

for (int i = 0; i < 10; i++)

{

if (array[i] < 0)

{

continue;

}

printf("%d ", array[i]);

}

return 0;

}


              123456789101112131415161718192021
            
#include <stdio.h> 

int main()
{
	int array[] = { 124, 235, -321, 32, 54, 
		           -549, 23445, 5534, -433 };

	printf("Positive elements of array:\n");

	for (int i = 0; i < 10; i++) 
	{
		if (array[i] < 0)
		{
			continue;
		}

		printf("%d ", array[i]);
	}

	return 0;
}

New Operators

The following operators can also function as expressions to update the counter:

Operator	Expression Example	Description
`+=`	`a += 5`	Equivalent to a = a + 5
`-=`	`a -= 5`	Equivalent to a = a - 5
`*=`	`a *= 5`	Equivalent to a = a * 5
`/=`	`a /= 5`	Equivalent to a = a / 5
`%=`	`a %= 5`	Equivalent to a = a % 5

War alles klar?

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Abschnitt 4. Kapitel 6

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