Format Specifiers, Width & Precision
beginner11 min readLesson 8 of 148
The full % vocabulary for the core types, plus minimum widths, zero padding, and decimal precision.
The % vocabulary
| Specifier | Prints | Example |
|---|---|---|
| %d | int (decimal) | 42 |
| %c | one character | A |
| %s | a C string | hi |
| %f | double, 6 decimals default | 3.141593 |
| %e | double, scientific | 3.141593e+00 |
| %zu | size_t (sizeof results) | 4 |
| %% | a literal percent | 50% |
Width and padding
A number between % and the letter sets a minimum width:
printf("[%5d]\n", 42); // [ 42] — right-aligned, space-padded
printf("[%-5d]\n", 42); // [42 ] — left-aligned
printf("[%05d]\n", 42); // [00042] — zero-padded
Precision
For %f, .N sets digits after the decimal point (rounding, not truncating):
printf("%.2f\n", 3.14159); // 3.14
printf("%.0f\n", 2.5); // 2 (banker's-ish rounding of exactly .5)
Combined: %8.2f = at least 8 characters wide, 2 decimals.