Chapter 2 Introduction to the C Language Objectives ❏ To

Chapter 2 Introduction to the C Language Objectives To understand the structure of a C-language program. To write your first C program. To introduce the include preprocessor command. To be able to create good identifiers for objects in a program. To be able to list, describe, and use the C basic data types. To be able to create and use variables and constants. To understand input and output concepts. To be able to use simple input and output statements. Computer Science: A Structured Programming Approach Using C 1

2-1 Background C is a structured programming language. It is considered a high-level language because it allows the programmer to concentrate on the problem at hand and not worry about the machine that the program will be using. That is another reason why it is used by software developers whose applications have to run on many different hardware platforms. Computer Science: A Structured Programming Approach Using C 2

2-2 C Programs It's time to write your first C program. Topics discussed in this section: Structure of a C Program Your First C Program Comments The Greeting Program Computer Science: A Structured Programming Approach Using C 3

FIGURE 2-2 Structure of a C Program Computer Science: A Structured Programming Approach Using C 4

FIGURE 2-3 The Greeting Program Computer Science: A Structured Programming Approach Using C 5

PROGRAM 2-1 The Greeting Program Computer Science: A Structured Programming Approach Using C 6

FIGURE 2-4 Examples of Block Comments Computer Science: A Structured Programming Approach Using C 7

FIGURE 2-5 Examples of Line Comments Computer Science: A Structured Programming Approach Using C 8

FIGURE 2-6 Nested Block Comments Are Invalid Computer Science: A Structured Programming Approach Using C 9

2-3 Identifiers One feature present in all computer languages is the identifier. Identifiers allow us to name data and other objects in the program. Each identified object in the computer is stored at a unique address. Computer Science: A Structured Programming Approach Using C 10

Table 2-1 Rules for Identifiers Computer Science: A Structured Programming Approach Using C 11

Note An identifier must start with a letter or underscore: it may not have a space or a hyphen. Computer Science: A Structured Programming Approach Using C 12

Note C is a case-sensitive language. Computer Science: A Structured Programming Approach Using C 13

Table 2-2 Examples of Valid and Invalid Names Computer Science: A Structured Programming Approach Using C 14

2-4 Types A type defines a set of values and a set of operations that can be applied on those values. Topics discussed in this section: Void Type Integral Type Floating-Point Types Computer Science: A Structured Programming Approach Using C 15

FIGURE 2-7 Data Types Computer Science: A Structured Programming Approach Using C 16

FIGURE 2-8 Character Types Computer Science: A Structured Programming Approach Using C 17

FIGURE 2-9 Integer Types Computer Science: A Structured Programming Approach Using C 18

Note sizeof (short) sizeof (int) sizeof (long) sizeof (long long) Computer Science: A Structured Programming Approach Using C 19

Table 2-3 Typical Integer Sizes and Values for Signed Integers Computer Science: A Structured Programming Approach Using C 20

FIGURE 2-10 Floating-point Types Computer Science: A Structured Programming Approach Using C 21

Note sizeof (float) sizeof (double) sizeof (long double) Computer Science: A Structured Programming Approach Using C 22

Table 2-4 Type Summary Computer Science: A Structured Programming Approach Using C 23

2-5 Variables Variables are named memory locations that have a type, such as integer or character, which is inherited from their type. The type determines the values that a variable may contain and the operations that may be used with its values. Topics discussed in this section: Variable Declaration Variable Initialization Computer Science: A Structured Programming Approach Using C 24

FIGURE 2-11 Variables Computer Science: A Structured Programming Approach Using C 25

Table 2-5 Examples of Variable Declarations and Definitions Computer Science: A Structured Programming Approach Using C 26

‘B’ FIGURE 2-12 Variable Initialization Computer Science: A Structured Programming Approach Using C 27

Note When a variable is defined, it is not initialized. We must initialize any variable requiring prescribed data when the function starts. Computer Science: A Structured Programming Approach Using C 28

PROGRAM 2-2 Print Sum of Three Numbers Computer Science: A Structured Programming Approach Using C 29

PROGRAM 2-2 Print Sum of Three Numbers (continued) Computer Science: A Structured Programming Approach Using C 30

PROGRAM 2-2 Print Sum of Three Numbers (continued) Computer Science: A Structured Programming Approach Using C 31

2-6 Constants Constants are data values during the execution of a constants have a type. In Boolean, character, integer, constants. that cannot be changed program. Like variables, this section, we discuss real, complex, and string Topics discussed in this section: Constant Representation Coding Constants Computer Science: A Structured Programming Approach Using C 32

Note A character constant is enclosed in single quotes. Computer Science: A Structured Programming Approach Using C 33

Table 2-6 Symbolic Names for Control Characters Computer Science: A Structured Programming Approach Using C 34

Table 2-7 Examples of Integer Constants Computer Science: A Structured Programming Approach Using C 35

Table 2-8 Examples of Real Constants Computer Science: A Structured Programming Approach Using C 36

FIGURE 2-13 Some Strings Computer Science: A Structured Programming Approach Using C 37

FIGURE 2-14 Null Characters and Null Strings Computer Science: A Structured Programming Approach Using C 38

Note Use single quotes for character constants. Use double quotes for string constants. Computer Science: A Structured Programming Approach Using C 39

PROGRAM 2-3 Memory Constants Computer Science: A Structured Programming Approach Using C 40

PROGRAM 2-3 Memory Constants (continued) Computer Science: A Structured Programming Approach Using C 41