Chapter 1. Introduction to Computers and Programming

1.1 Why Program? Computers can do many different jobs because they are programmable.

1.2 Computer Systems: Hardware and Software All computer systems consist of similar hardware devices and software components. This section provides an overview of standard computer hardware and software organization.

Hardware The CPU Main Memory Secondary Storage Input Devices Output Devices

Figure 1.1 Central Processing Input Unit Device Output Device Main Memory Output Device

Arithmetic and Logic Unit Figure 1.2 Instruction (Input) Arithmetic and Logic Unit Result (Output) Control Unit

Software Operating Systems Application Software Single tasking Multi-tasking Application Software

1.3 Programs and Programming Languages What is a program? A set of instructions a computer follows in order to perform a task. A programming language is a special language used to write computer programs.

Program 1-1 // This program calculates the user’s pay. #include <iostream.h> void main(void) { float hours, rate, pay; cout << “How many hours did you work? ”; cin >> hours; cout << “How much do you get paid per hour? ”; cin >> rate; pay = hours * rate; cout.precision(2); cout.setf(ios::fixed | ios::showpoint); cout << “You have earned $” << pay << endl; }

Program Output How many hours did you work? 10 How much do you get paid per hour? 15 You have earned $150.00

Programming Languages Figure 1-4 High level (Close to Human Language) Low level (Machine Language)

Table 1-1

1.4 What is a Program Made of? There are certain elements that are common to all programming languages. Key Words Programmer-Defined Symbols Operators Punctuation

Language Elements, Table 1-2

Lines and Statements cout << “How many hours did you work?”;

Variables A storage location in the computer’s memory for holding a piece of information. Symbolic names that represent locations in the computer’s random-access memory.

Variable Declarations Two types of information: numbers and characters Numbers may be integers or floating-point numbers The statement below creates three variables in memory named hours, rate, and pay that each can store a floating point number float hours, rate, pay;

1.5 Input, Processing, and Output cin >> hours; Processing: pay = hours * rate; Output cout<<“You have earned $”<<pay;

1.6 The Programming Process The programming process consists of several steps, which include design, creation, testing and debugging activities.

Designing and Creating a Program 1. Clearly define what the program is to do 2. Visualize the program running on the computer. 3. Design a hierarchy chart 4. Check the hierarchy chart for logical errors.

5. Write a pseudocode version of the program. 6. Check the pseudocode for errors. 7. Write the actual program on paper. 8. Desk-check the program for errors. 9. Enter the code and compile it. 10. Correct any errors found during compilation. Repeat steps 9 and 10 as many times as necessary.

11. Run the program with test data for input. 12. Correct any errors found while running the program. Repeat steps 9 through 12 as many times as necessary.

1.7 Procedural and Object-Oriented Programming Procedural programming and object-oriented programming are two ways of thinking about software development and program design.