Programming Concepts (Part A) ENGR 10 Introduction to Engineering pot

A computer program is an ordered list of instructions.. Consider the sequential execution of the above expressions to find the value of y:... An Empty EasyC programC programFlow chart Y

Programming Concepts

(Part A)

ENGR 10 Introduction to Engineering

What is a program?

WHITE CAKE RECIPE

1 Preheat oven to 350 degrees F (175 degrees C)

2 Grease and flour a 9x9 inch pan.

3. In a medium bowl, cream together the sugar and butter.

4 Beat in the eggs.

5 Stir in the vanilla

6 Combine flour and baking powder, add to the creamed mixture and mix well

7 Stir in the milk until batter is smooth

8 Pour or spoon batter into the prepared pan

9 Bake for 30 to 40 minutes in the preheated oven

A computer program is an ordered

list of instructions.

It’s like a recipe!

In Summary…

(3a 2 + 21) / b + 4

Sequential Solving

following Math conventions for correct answer.

Consider the sequential execution of the above expressions to find the value of y:

An Empty EasyC program

C programFlow chart

Your program goes

C program

Logic flow

An instruction

in C

• A “variable” is a place where we keep a value.

A = 10 ; // The value 10 is stored in A.

• Any statement after the sign “//” is NOT part of the program It is a comment made by the programmer.

WSalary = 800 ; // Any statement can go here.

• A semicolon is required at the end of each C

instruction

Variables, cont.

Every variable in the program needs to be

declared in the beginning of the program

Commonly Used Variable Types

Variable

extended range EX: 56, 6000, -4,234,128

-2,147,483,648 to +2,147,483,647

float Stores values with decimal

point EX: 1.245, -4.2341

[-10^+38, -10^-38] 0

[10^-38, 10^+38]

• Global Variable:

This variable is accessible from

anywhere within your program

• Local Variable:

This variable is only accessible from a

“local area” within your program (“functions” will be discussed later)

Global Variable Declaration

To declare a global variable, click on the tab

“Global” in the Main program

Global Variable Declaration

(A close-up view)

Assignment Operator

• In C language “ = ” is an assignment operator, not an “ is equal to ” statement.

• A = 10; // means assign 10 to A.

• A = B; // means assign the value of B to A

• A = A+1; //means assign the value A+1

// back to A, i.e., increase A by 1.

Assignment Operator: Examples:

int A; // a variable named A of type integer

int B; // a variable named B of type integer

A = 10; // value 10 is assigned to variable A

Q1: What is the value of B at the

end of this program?

Decision Making

• The ability to make decision is the most basic form of

intelligence.

• A linear (sequential) execution of instructions can only

perform a simple task that does not involve decision

making.

• The IF instruction gives a C program decision making ability

IF Statement: Simple Example

This == symbol is used for

checking ‘equal’ condition,

not for value assignment.

Only if this condition is true, this instruction is executed.

IF-ELSE StatementConsider the following program:

If (score <60)

{ PrintToScreen(“You failed the test”);}

If (score == 60) // ‘==‘ means ‘if equal to’{ PrintToScreen(“You passed the test”);}

If (score > 60)

{ PrintToScreen(“You passed the test”);}

Q2: What is the value of A and B

at end of this program?

WHILE Statement

• In C, the WHILE statement is useful for

repeating a set of instructions

Suppose we have to add the first 50 positive integers

1+2+3+4+………+48+49+50

First Approach:

Use a single statement:

int SUM ; // integer variable for the resultSUM = 1+2+3+……… +48+49+50;

Second Approach:

int SUM ; //variable SUM is declared as integer SUM = 0 ; //SUM is assigned the value 0

SUM = SUM + 1 ; // Now SUM = (0 + 1) = 1

SUM = SUM + 2 ; // SUM = (1 + 2) = 3

SUM = SUM + 3 ; // SUM = (3 + 3) = 6

SUM = SUM + 49 ; //SUM = (1176 + 49) = 1225 SUM = SUM + 50; //SUM = (1225 + 50) = 1275

Third approach:

Use “while” statement

This condition is checked first If it is true, the block

While Statement - Example

• To find factorial of a number N

Q3: What is the final value of A

Fourth iteration : condition 3<3 is false

So the WHILE loop stops.

Final Value of A is 3.

Infinite Loop

• In the previous examples we have employed

condition checking in order to control the flow of

• The status of a bumper switch is continuously

monitored and depending on its value the

movement of the robot is decided.

while (1==1)

{ status = GetDigitalInput(5); // read bumper

if (status ==1 ) // bumper hits something

{ SetMotor(2,127);} // Stop the robot

else

{ SetMotor(2,0); // Move forward

} }

Infinite Loop

The status of a bumper switch (via Digital input port #5) is repeatedly read needlessly When a hit (status==1) is detected, the robot is stopped

status = GetDigitalInput(5); // read bumper

while (1==1)

{

if (status ==1 ) // bumper hits something

{ SetMotor(2,127);} // Stop the robot

else

{ SetMotor(2,0); // Move forward

} }

Infinite Loop

A common mistake – reading sensor OUTSIDE of the loop

IMPORTANT NOTE

Review this example carefully