Variable Declarations in C language

Before you can use a variable in a C program, it must be declared. A variable declaration tells the compiler the name and type of a variable and optionally initializes the variable to a specific value. If your program attempts to use a variable that hasn't been declared, the compiler generates an error message. A variable declaration has the following form:

typename varname;

typename specifies the variable type and must be one of the keywords listed in Table 3.2. varname is the variable name, which must follow the rules mentioned earlier. You can declare multiple variables of the same type on one line by separating the variable names with commas:

int count, number, start;    /* three integer variables */
float percent, total;        /* two float variables */

On Day 12, "Understanding Variable Scope," you'll learn that the location of variable declarations in the source code is important, because it affects the ways in which your program can use the variables. For now, you can place all the variable declarations together just before the start of the main() function.