Reserved Words
The identifiers listed below are reserved C keywords. You shouldn’t use them for any other purpose in a C program. They are allowed, of course, within double quotation marks.
Reserved C keywords:
| Keyword | Description |
| asm | Keyword that denotes inline assembly language code. |
| auto | The default storage class. |
| break | Command that exits for, while, switch, and do…while statements unconditionally. |
| case | Command used within the switch statement. |
| char | The simplest C data type. |
| const | Data modifier that prevents a variable from being changed. See volatile. |
| continue | Command that resets a for, while, or do…while statement to the next iteration. |
| default | Command used within the switch statement to catch any instances not specified with a case statement. |
| do | Looping command used in conjunction with the while statement. The loop will always execute at least once. |
| double | Data type that can hold double-precision floating-point values. |
| else | Statement signaling alternative statements to be executed when an if statement evaluates to FALSE. |
| enum | Data type that allows variables to be declared that accept only certain values. |
| extern | Data modifier indicating that a variable will be declared in another area of the program. |
| float | Data type used for floating-point numbers. |
| for | Looping command that contains initialization, incrementation, and conditional sections. |
| goto | Command that causes a jump to a predefined label. |
| if | Command used to change program flow based on a TRUE/FALSE decision. |
| int | Data type used to hold integer values. |
| long | Data type used to hold larger integer values than int. |
| register | Storage modifier that specifies that a variable should be stored in a register if possible. |
| return | Command that causes program flow to exit from the current function and return to the calling function. It can also be used to return a single value. |
| short | Data type used to hold integers. It isn’t commonly used, and it’s the same size as an int on most computers. |
| signed | Modifier used to signify that a variable can have both positive and negative values. See unsigned. |
| sizeof | Operator that returns the size of the item in bytes. |
| static | Modifier used to signify that the compiler should retain the variable’s value. |
| struct | Keyword used to combine C variables of any data type into a group. |
| switch | Command used to change program flow in a multitude of directions. Used in conjunction with the case statement. |
| typedef | Modifier used to create new names for existing variable and function types. |
| union | Keyword used to allow multiple variables to share the same memory space. |
| unsigned | Modifier used to signify that a variable will contain only positive values. See signed. |
| void | Keyword used to signify either that a function doesn’t return anything or that a pointer being used is considered generic or able to point to any data type. |
| volatile | Modifier that signifies that a variable can be changed. See const. |
| while | Looping statement that executes a section of code as long as a condition remains TRUE. |
