K Hinds Section No.2 Problem-Solving and Program Design12

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1 Section No.2 Problem-Solving and Program Design12 Problem Solving To model a program with utility to a problem, we need to implement a number of processes prior to actually writing any code in any programming language. We break up these processes into two general phases: Note: Algorithm: This is a set of precise instructions that results in a solution Phase 1: Algorithm Phase 1. Clearly define the problem to be solved 2. Design an algorithm to solve problem 3. Test algorithm on paper 1

2 Phase 2: Implementation Phase 1. Translate Program into Programming Language i.e. Pascal 2. Test Program for consistency 3. Document/Comment inside the program and produce a manual for how the program works 4. Specify Storage so that the data can be stored temporarily during the processing stage PHASE No.1 1. Defining the Problem To correctly define the problem, we need to clearly specify the objectives of the program using the recommended 3-step approach: Specify Output Specify Input Specify Processing Steps We also use Input-Output-Processing (IPO) charts at this point to graphically present the issue with the solutions. Suggestion An ideal method is to start first with what is required by the program and list them on the input line/ Secondly, list the Outcome of the program on the Output line and finally, list the steps necessary to achieve the outcome. E.g. Input Processing Output List all input items needed List processing steps. Start with gathering input from user, process user data and storage for passing to output List expected Outcomes Homework/Classwork Page 54 Questions 1-9: Information Technology for CSEC. Glenda Gay and Ronald Blades 2

3 2. Designing an Algorithm Remember: An algorithm is a set of precise instructions that yields the solution to a given problem. It is usually written in Pseudocode or Pseudo-English English like statements that give clear instructions on what is required to achieve an outcome in a language that is easily understood. General Format for Pseudocode: PROGRAM: Insert Program Name Processing Processing END PROGRAM Characteristics of a good Algorithm Correct: Accept valid and invalid inputs and still give meaningful information Simple: Each step should perform one logical step in solving problem Clear: Easy to read and understand Precise: No programming code should be present. Each step should be clearly stated in English Easy to implement: Should translate easily into any programming language Efficient: Uses the best method of solving a problem NORMALLY, the Algorithm is used to supplement the IPO. Pseudocode Pseudocode utilizes an informal manner in providing a solution to a problem WITHOUT coding the solution in a programming language. Pseudocode is different because we can use some programming operators language independent here. Statements and keywords: Related lines of code for a statement. Instructions within the statement are called keywords. o Statements can be sequential executed only once or conditional; executed until some condition is met e.g. IF, THEN; DO WHILE o Keywords are inbuilt words that the system has predefined for some function eq: PRINT or IF-THEN, etc. Variables: Stores data for the program to work with; text or numbers o Global Variable are used throughout the entire program. The contents may change through each function; in which case it becomes a local variable at that point only - but all functions have access to the variable 3

4 Flow Charts o Flow Charts helps us to visualize a problem into graphical format. Basic building blocks for a Flow Chart are: Conditional Statements: These provide choice based on possible outcomes of some logical operator o IF Statement IF (Condition) THEN <Do Something (s) if True>ENDIF 4

5 o IF-THEN-ELSE Statement IF(Condition) THEN <Do Something if True>ELSE<Do Something if False>ENDIF Loops: Executes the same part of a program until some condition is met; WHILE-DO, REPEAT-UNTIL & FOR. o WHILE-DO WHILE (Condition) DO BEGIN <Statement(s)> END 5

6 o REPEAT-UNTIL REPEAT <Statement(s)> <Statement(s)> UNTIL (Condition) o FOR FOR (Variable := <Start Value) TO/DOWNTO (Final Value) DO BEGIN <Statement (1)> <Statement (2)>. <Statement (n)> END Arithmetic and Logical Operators o +, -, /, *, >, <, <>, ^, %, >=, <=, <>, =, TRUE, FALSE, Subroutine: Groups a part of the program together 6

7 Binary Counting in 2 bits, 3-bits & 4-bits Adding in Binary; 1+0 = 1; = 0; = 10 ; = 11 Logic Gates 7

Introduction to Computer Programming/Handout 01 Page 1 of 13

Introduction to Computer Programming/Handout 01 Page 1 of 13 Table of Contents Table of Contents... 1 Learning Objectives... 2 Program... 2 Programmer... 2 Programming Language... 2 Types of Languages...