Relearning C - Chapter 2

Chapter 2 - Types, Operators and Expressions

Variables and constants are the basic data objects manipulated in a program. Declarations list the variables to be used, and state what type they have and perhaps what their initial values are. Operators specify what is to be done to them. Expressions combine variables and constants to produce new values. The type of an object determines the set of values it can have and what operations can be performed on it. These building blocks are the topic of this chapter.

2.2 Data Types and Sizes

In addition, there are a number of qualifiers that can be applied to these basic types. short and long apply to integers.

short int sh;
long int counter;

The word int can be omitted in such declarations, and typically it is.

short is often 16 bits long, and int is either 16 or 32 bits long. long is at least 32 bits, and short is no longer than int, which is no longer than long. The qualifier signed or unsigned may be applied to char or any integer. unsigned numbers are always positive or zero, and obey the laws of arithmetic modulo 2^n, where n is the number of bits in the type.

The standard headers <limits.h> and <float.h> contain symbolic constants for all of these sizes, along with other properties of the machine and compiler.

2.9 Bitwise Operators

C provides six operators for bit manipulation. These can only be applied to char, short, int, and long. Whether signed or unsigned.

2.11 Conditional Expressions

Exercise 2-10. Rewrite the function lower, which converts upper case letters to lower case, with a conditional expression instead of if-else.

int lower(int c) {
    return (c >= 'A' && c <= 'Z') ? (c + 'a' - 'A') : c;
}