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## Structured Program Development

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Title: Structured Program Development

1
Structured Program Development
• Dilshad M. Shahid
• New York University
• _at_1998

2
Today
• Float Variables
• How to use Borland
• Equality and Relational Operators
• Algorithms
• Pseudocode
• Control Structures

3
Float variables
• Float Data Type Data Type that can hold numbers
with decimal values e.g. 5.14, 3.14
• Float example

4
• / Float Example Program /
• include ltstdio.hgt
• main ()
• float var1, var2, var3, sum
• var1 87.25
• var2 92.50
• var3 96.75
• sum var1 var2 var3
• printf(Sum .2f, sum)
• getchar()

5
How to use Borland C
• Borland comes with 3 disks. Please use the 5.0
disk.
• ACF labs have correct version installed
• A new text page automatically when you open
Borland
• Alternatively, you can go to menu option File,
then New, then Text Edit

6
More Borland
• Use Save As to save to your disk on the A\ drive
• After you type in your program, there are 3 ways
to compile
• click lightning bolt
• go to menu option Debug, then Run
• Hit Control-F9

7
Relational and equality operators
• table adapted from Figure 2.12, pg 38
• standard algebraic in C example in C meaning of C
condition
• Equality x y x is equal to y
• ! x ! y x is not equal to y
• Relational gt gt x gt y x is greater than y
• lt lt x lt y x is less than y
• gt gt x gt y x is greater than or equal to y
• lt lt x lt y x is less than or equal to y

8
Algorithms
• Algorithm the procedure for solving a problem
in terms of
• the actions to be executed
• the order in which these actions are to be
executed.
• See pages 56 to 57 for a more detailed
description.

9
Pseudocode
• Pseudocode this is simply writing your code in
ordinary English to help yourself develop an
algorithm that will be converted into a
structured C program.
• More examples in the text book

10
Control structures
• All programs can be written in terms of only 3
control structures
• sequence structure
• selection structure
• repetition structure

11
Sequence structure
• This is essentially built into C
• Unless directed otherwise, the computer will
automatically execute C statements one after
another in the order in which they are written
• This is called sequential execution

12
Selection structure
• A selection structure will perform an action
based on the conditions it receives
• 3 kinds of selection structures in C
• if
• if/else
• switch

13
If statement
• Performs indicated action only when condition is
true otherwise the action is skipped.
• Example in pseudocode
• If bank balance is less than 100
• Print You are below the required minimum

14
If statement
• Same example in C
• int balance
• balance 90
• if (balance lt 100)
• printf(You are below the required minimum
balance\n)
• What will the output be? Change the program so
that balance 110. What will the output be in
this case?
• Answer You are below the required minimum
balance
• No output.

15
If/else statement
• Programmer can specify that different actions are
to be performed when the condition is true than
when the condition is false

16
If/else statement
• Example in pseudocode
• If bank balance is less than 100
• Print You are below the required minimum
• else
• Print You may withdraw money

17
If/else statement
• Same example in C
• int balance
• balance 90
• if (balance lt 100)
• printf(You are below the required minimum
balance\n)
• else
• printf(You may withdraw money\n)
• Make balance equal 120, i.e. greater than 100.
What will the output be?

18
If/else statement
• Another example in C
• int age
• float height
• age 10
• height 5.0
• if (height gt 4.0) / must have 4.0, it is
float/
• printf(Your height is f\n, height)
• else
• printf(Your age is d\n, age)
• What will output be if height 4.0 ? Does
changing value of age affect the program output?