Understanding variables is essential to C as well as objective-C. They are used the same in each language.

A variable is a word that refers to something such as a number or a word.

C includes the following fundamental data types:

type use size range

---

char character 8 bits -128 to 127 unsigned char character 8 bits 0 to 255 short integer 16 bits -32,768 to 32,767 unsigned short integer 16 bits 0 to 65,535 int integer 32 bits -32,768 to 32,767 unsigned int integer 32 bits 0 to 65,535 long integer 32 bits -2,147,483,648 to 2,147,483,647 unsigned long integer 32 bits 0 to 4,294,967,295 float real 32 bits 1.2E-38 to 3.4E+38 double real 64 bits 2.2E-308 to 1.8E+308 long double real 128 bits 3.4E-4932 to 1.2E+4932

(Be aware that these may change in the future, for example on the 64-bit PowerPC in the GeeFive. Rest assured, they’ll only get bigger.)

When referring to variables in certain functions you can use the following codes (Objective-C adds the last one):

• %d for integer
• %c for a single character
• %F for a double number
• %s for a string this reads in a single word
• %@ for an object (including NSStrings)

See also HowToUsePointers

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