Algorithms and Flowcharts Lecture Notes PDF

ALGORITHMS AND FLOWCHARTS Lecture 1: Problem Analysis By: Ashutosh Mishra  ALGORITHMS AND FLOWCHARTS A typical programming task can be divided into two phases: Problem solving phase  produce an ordered sequence of steps that describe solution of problem...

ALGORITHMS AND FLOWCHARTS Lecture 1: Problem Analysis By: Ashutosh Mishra  ALGORITHMS AND FLOWCHARTS A typical programming task can be divided into two phases: Problem solving phase  produce an ordered sequence of steps that describe solution of problem  this sequence of steps is called an algorithm Implementation phase  implement the program in some programming language  Steps in Problem Solving First produce a general algorithm (one can use pseudocode) Refine the algorithm successively to get step by step detailed algorithm that is very close to a computer language. Pseudocode is an artificial and informal language that helps programmers develop algorithms. Pseudocode is very similar to everyday English.  Pseudocode & Algorithm Example 1: Write an algorithm to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four marks.  Pseudocode & Algorithm Pseudocode: Input a set of 4 marks Calculate their average by summing and dividing by 4 if average is below 50 Print “FAIL” else Print “PASS”  Pseudocode & Algorithm Detailed Algorithm Step 1: Input M1,M2,M3,M4 Step 2: GRADE  (M1+M2+M3+M4)/4 Step 3: if (GRADE < 50) then Print “FAIL” else Print “PASS” endif  The Flowchart (Dictionary) A schematic representation of a sequence of operations, as in a manufacturing process or computer program. (Technical) A graphical representation of the sequence of operations in an information system or program.  Information system flowcharts show how data flows from source documents through the computer to final distribution to users.  Program flowcharts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flowchart.  The Flowchart A Flowchart  shows logic of an algorithm  emphasizes individual steps and their interconnections  e.g. control flow from one action to the next  Flowchart Symbols Basic Name Symbol Use in Flowchart Oval Denotes the beginning or end of the program Parallelogram Denotes an input operation Rectangle Denotes a process to be carried out e.g. addition, subtraction, division etc. Diamond Denotes a decision (or branch) to be made. The program should continue along one of two routes. (e.g. IF/THEN/ELSE) Hybrid Denotes an output operation Flow line Denotes the direction of logic flow in the program  Example START Step 1: Input M1,M2,M3,M4 Step 2: GRADE  (M1+M2+M3+M4)/4 Input M1,M2,M3,M4 Step 3: if (GRADE