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Constants

Constants

Learn about different types of constants in C.

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Constants are values that do not change after they have been defined. These values can be of different types.

Numeric constants

An example of an int constant is the number 1234. An example of a floating-point constant (by default typed as a double) is 123.4. Another example of a floating-point constant is 2e-3 (which represents 2 x 10-3 in scientific notation). We can also write numbers in octal or hexadecimal representations instead of decimal: octal by using a leading zero (0) and hexadecimal by using a leading zero followed by an x (0x). Decimal 31 can be written as 037 in octal and 0x1f or 0X1F in hexadecimal. Here are some examples of how numeric constants are created and then assigned to variables:

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int year = 1984;       // integer constant 1984
int octalYear = 03700; // 1984 in octal
int hexYear = 0x7c0;   // 1984 in hexadecimal

Here is some code to show how to print integers in various representations. Execute the following code.

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#include <stdio.h>
int main(void) {
  printf("1984 in decimal is %d\n", 1984);
  printf("1984 in octal is 0%o\n", 1984);
  printf("1984 in hexadecimal is 0x%x\n", 1984);
  printf("0123 is octal for %d\n", 0123);
  printf("0x12f is hexadecimal for %d\n", 0x12f);
  return 0;
}

Character constants

A character constant is written between single quotes, for example, 'x'. Characters in C are actually represented using integer values, from the ASCII character set. ASCII codes range between 0 and 255. The upper-case alphabet ...