Zero Padding in C with printf#

In C, printf() can add leading zeros to make a number occupy a fixed minimum width.

The syntax is:

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%0<width><specifier>

For example:

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printf("%06d", 123);

Output:

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000123

Here:

• 0 → pad with zeros
• 6 → minimum field width is 6 characters
• d → print a signed decimal integer

Zero padding vs space padding#

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printf("%06d", 123);

Output:

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000123

while:

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printf("%6d", 123);

Output:

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   123

So:

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2

%06d → zero padding
%6d  → space padding

Example: hexadecimal#

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printf("0x%08lx\n", value);

For:

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value = 0x1234;

the output is:

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0x00001234

%08lx means:

• 0 → zero padding
• 8 → minimum width of 8 characters
• l → long
• x → hexadecimal

Zero padding is useful when displaying IDs, hexadecimal values, timestamps, counters, or other fixed-width numbers where aligned output is desirable.