Programming

1. Programming

2. Objectives • Define the term program • List and explain the steps involved in developing a program

3. Introduction • How are instructions given to the computer? • Computer programs – finite set of precise instructions written in a computer language • Before program is written we must find a way to solve the problem • After figuring out how to solve the problem we then translate the solution into a language meaningful to the computer

4. Introduction • Giving precise, unambiguous instructions is not inherent in human nature • Consider the following: Proceed a mile or so down the road until you reach the roundabout. Turn left at the roundabout and follow the road until you reach a green house on the right hand side. The Post office is about the 3rd or 4th building on the right after the green house. You can’t miss it!

5. Introduction • Examples of everyday problems: • Write a recipe for making a cheese sandwich • Write instructions to teach your mom how to retrieve voice message from a generic cell phone • Write instructions to give directions to a visitor to get to the nearest hospital, starting from the school premises • Write instructions to tell your grandparent how to download music from the Internet.

6. Problem solving on the Computer • The design of any computer program involves two phases: • The Problem-solving Phase • The Implementation Phase

7. The Problem Solving Phase • Define the problem • Analyze the problem • Develop an algorithm or method for solving the problem • Choose a programming language

8. The Implementation Phase • Write the computer program which implements the algorithm in the chosen programming language • Test and debug the program • Document the program • Maintain the program

9. Phase One Problem Solving Phase

10. Defining the Problem • Stating exactly what the program must do or achieve. • Defining the problem is the first step towards finding a solution. • It helps the programmer to understand what is given and what is required. • If the programmer does not fully understand what is required, he/she cannot produce the desired solution to the problem

11. Calculate and print the sum of two numbers. • Compute the average Age of a class • Grade the scores of students in an examination • Calculate the amount due for an item based on the quantity purchased and the price. • Calculate and print the revenue made by a minibus which made 20 trips from Castries to Gros Islet. Each passenger paid $1.50. If the revenue for the day exceeded $500 a bonus of 10% of the revenue is given to the driver. Compute the bonus amount.

12. Analyze the Problem • In order to find a solution to a problem each operation must be identified together with the sequence of performing them. • The process of finding out the operations is known as analyzing the problem. This involves: • Ensuring that there is the clearest possible understanding of it. • Determining the general requirements such as what input is needed, processing required, output needed and storage required. • Consider alternative solutions

13. Develop an Algorithm • An algorithm is a set of instructions which if followed will produce a solution to a given problem or perform a specified task. • The instructions in the algorithm must be written in a form the computer can understand. Computer program instructions fall into three main categories: • Input instructions: used for supplying data from the outside world to a program • Processing instructions: used for manipulating data inside the computer- to add, subtract, multiply, and divide, compare values. • Output instructions: used for getting instructions out of the computer

14. Choose the Appropriate Programming Language • In order to write a program a suitable programming language must be chosen. • A program is a set of instructions written in a particular programming language which when executed will produce a solution to a given problem or perform a specified task.

15. The main difference between an algorithm and a program is that an algorithm can be written in informal language without having to follow special rules whereas the program is written in a programming language and must follow all the syntax rules of the language.

16. A program written in Pascal is referred to as a source program orsource code, because Pascal is a high level language. • Other high level languages include Fortran (Formula Translation), COBOL (Common Business Oriented Language), BASIC (Beginner's All-purpose Symbolic Instruction Code) and C.

17. However computers are built to execute instructions written in what is called machine language. • In machine language everything is expressed in terms of the binary number system – 1’s and 0’s. • Machine language is considered a low level programming language.

18. Therefore even programs written in a high level language must be translated into machine language so that the computer can understand. Compilers are used to translate high level languages into machine language.

19. Questions • What makes it possible to do a variety of things on a computer? • Computers can execute instructions written in what language? • Describe the steps which must be performed for a problem to be solved by a computer? • Distinguish between an algorithm and a program.

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