Chapter 1. Introduction to Computers and Programming

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Chapter 1. Introduction to Computers and
Programming
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1.1 Why Program?

• Computers can do many different jobs because they
  are programmable.

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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.

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Hardware

1. The CPU
2. Main Memory
3. Secondary Storage
4. Input Devices
5. Output Devices

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Figure 1.1
Central Processing Unit
Input Device
Output Device
Main Memory
Output Device
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Figure 1.2
Arithmetic and Logic Unit
Instruction (Input)
Result (Output)
Control Unit
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Software

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

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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.

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Program 1-1

• // This program calculates the users pay.
• include ltiostream.hgt
• void main(void)
• float hours, rate, pay
• cout ltlt How many hours did you work?
• cin gtgt hours
• cout ltlt How much do you get paid per hour?
• cin gtgt rate
• pay hours rate
• cout ltlt You have earned ltlt pay ltlt endl

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Program Output

• How many hours did you work? 10
• How much do you get paid per hour? 15
• You have earned 150

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Programming Languages

• Figure 1-4

High level (Close to Human Language)
Low level (Machine Language)
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Table 1-1
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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

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Language Elements, Table 1-2
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Lines and Statements

• cout ltlt How many hours did you work?

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Variables

• A storage location in the computers memory for
  holding a piece of information.
• Symbolic names that represent locations in the
  computers random-access memory.

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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

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1.5 Input, Processing, and Output

• Input
• cin gtgt hours
• Processing
• pay hours rate
• Output
• coutltltYou have earned ltltpay

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1.6 The Programming Process

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

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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 flowchart or hierarchy chart
• 4. Check the flowchart or hierarchy chart for
  logical errors.

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• 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.

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

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1.7 Procedural and Object-Oriented Programming

• Procedural programming and object-oriented
  programming are two ways of thinking about
  software development and program design.