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Control Statements-1 Algorithms and Pseudocode

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Control Statements-1 Algorithms and Pseudocode ECE 114 - 3 Control Statements-1 Dr. Z. Aliyazicioglu Cal Poly Pomona Electrical & Computer Engineering Cal Poly Pomona Electrical & Computer Engineering 1 Algorithms and Pseudocode A procedure for solving a problem in terms of – The actions to be executed and – The order in which these actions are to be executed This is called an algorithm Pseudocode is an artificial and informal language that helps programmers develop algorithms. Similar to spoken language It is not executed on the computer Decribes only executable statement Cal Poly Pomona ECE 114-3 2 1 Control Structure MC++ has seven control structures – One sequence structure (sequential execution) – Three types of selection structure and – Three types of repetition structure In MC++, selection structures are created with selection statements. MC++ provides three types of selection statements – if selection statement – if … else selection statement – switch selection statements Cal Poly Pomona ECE 114-3 3 Control Structure The if selection statement is called a single-selection structure It selects or ignores a single action (group of actions) The if…else statement is called a double selection structure It selects between two different action (group of actions) The switch statement is called a multiple-selection structure. It select among of different actions (group of actions) Cal Poly Pomona ECE 114-3 4 2 Control Structure In MC++, repetation structures are created with repetation statement MC++ provides three repetition statement – while – do…while – For We will talk about them later Cal Poly Pomona ECE 114-3 5 if Selection Statement If selection structure perform an indicated action only when the condition is true otherwise the action is skipped Example: Let’s have pseudocode statement » If student’s grade is greater than or equal to 60 » Print “Passed” if (studentGarde >=60) Console::WriteLine( S”Passed” ); if (Exp) True { studentGrade>=60 Print”Passed” ….. } False Cal Poly Pomona ECE 114-3 6 3 The if…else Selection Structure The if…else selection structure allows the programmer to specify that different action is to be performed when condition is true and when the condition is false Example: false true Grade>=60 if (grade >= 60) Console:: WriteLine( S”Passed”); else Print”Failed” Print”Passed” Console:: WriteLine( S”Failed”); Cal Poly Pomona ECE 114-3 7 Conditional Operator C++ has conditional operator (?:) that is closely related to the if…else structure Console::WriteLine (grade >=60 ? ”Passed” : ”Failed”); Cal Poly Pomona ECE 114-3 8 4 Nested if …else Statement Nested if…else structure test for multiple cases by placing if…else selection structures inside if…else selection structure if (grade >= 90) Console::WriteLine ( S”A” ); else if (grade >= 80) Console::WriteLine ( S”B” ); else if (grade >= 70) Console::WriteLine ( S”C” ); else if (grade >= 60) Console::WriteLine ( S”D” ); else Console::WriteLine ( S”F” ); Cal Poly Pomona ECE 114-3 9 Example The following example includes a compound statement in else part of the if…else structure if (grade >= 60) Console::WriteLine ( S”Passed.”); else { Console::WriteLine ( S”Failed.”); Console::WriteLine ( S”You must take this course again.”); } Cal Poly Pomona ECE 114-3 10 5 Example if (x >5 Wrong if (y>5) representation Console::WriteLine ( S”x any y are <=5.”); else Console::WriteLine ( S”x is <=5.”); if (x >5 Right if (y>5) representation Console::WriteLine ( S”x any y are <=5.”); else Console::WriteLine ( S”x is <=5.”); Cal Poly Pomona ECE 114-3 11 Example If originally x=2, y=3, z=4, what is the value of x, y, and z after executing the following code? if (z > x) if ( y > z) { x=x+ 3; y =y-1; } else { x= y + z + 1; y++; } else x = z + y; Cal Poly Pomona ECE 114-3 12 6 The while Repetition Structure A repetition structure allows the programmer to specify that an action is to be repeated while some condition remains true. initialization initialization; while (loop test) { test Statements statements; increment; } Cal Poly Pomona ECE 114-3 13 Examples: int product = 2; while (product <= 1000) { product =2*product; Console::WriteLine ( S”Product={0},product.ToString()”); } x=1; while (x<=20) { x=x+3; Console::WriteLine ( S”x={0},x.ToString()”); } Cal Poly Pomona ECE 114-3 14 7 Example // Class Average with counter-controlled repetation #include "stdafx.h" #using <mscorlib.dll> using namespace System; int _tmain() { int total, // sum of grades gradeCounter, // number of grades to be entered gradeValue, // grade value average; //average of grades // initialization phase total = 0; // clear total gradeCounter = 1; // prepare to loop Cal Poly Pomona ECE 114-3 15 Example (Cont.) // processing phase while (gradeCounter <=10) { Console::WriteLine( S"Enter integer grade : "); gradeValue =Int32::Parse( Console::ReadLine() ); total = total + gradeValue; //add garde to total gradeCounter = gradeCounter + 1; //increment counter } // termination phase average = total / 10; //integer division Console::WriteLine( S"Class average is {0}, average.ToString()"); return 0; } Cal Poly Pomona ECE 114-3 16 8.
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