Chapter 1. Introduction to Computers and Programming

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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 SoftwareAll computer systems consist of similar hardware devices and software components. This section provides an overview of standard computer hardware and software organization.


HardwareThe CPU Main Memory Secondary Storage Input Devices Output Devices


Figure 1.1Input DeviceCentral Processing UnitMain MemoryOutput DeviceOutput Device


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


SoftwareOperating Systems Single tasking Multi-tasking Application Software


1.3 Programs and Programming LanguagesWhat 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 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 << “You have earned $” << pay << endl; }


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


Programming LanguagesFigure 1-4High 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 Statementscout << “How many hours did you work?”;


VariablesA 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 DeclarationsTwo 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 OutputInput: cin >> hours; Processing: pay = hours * rate; Output cout<<“You have earned $”<


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


Designing and Creating a Program1. 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.


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. Correct any errors found while running the program. Repeat steps 9 through 12 as many times as necessary. Validate the results of the program.


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

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Last Updated: 8th March 2018

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