Introduction to Programming in C

1
Chapter 2

• Introduction to Programming in C

2
Hello World Program

• / Program 1 - A first Program. Multiline
  Comments
• Name D.L. Sonnier
• Class CSC 140
• Date 25 August 2006
• PLEDGED
• /
• include Header
• Access to standard library
• //main() is where program execution begins.
  Single Line Comment
• main()
• main() begins here
• printf ("Hello World.\n") console output
• main() ends here

3
Program Compile and Run

• ab1234compscilab cc prog1.c
• ab1234compscilab ./a.out
• Also
• ab1234compscilab gcc prog1.c
• ab1234compscilab ./a.out
• To compile to an executable by the name of
  something other than a.out, do
• ab1234compscilab cc -o prog1 prog1.c
• ab1234compscilab ./prog1

4
Program General Form

• / Program X - Description
• Name D.L. Sonnier
• Class CSC 140
• Date
• PLEDGED
• /
• include
• directives
• //Description
• main()
• statements

5
Return Statement

• include
• main()
• printf ("Hello World.\n")
• return 0
• Note main() is a function, and as such it
  should always return a value. Make this return
  statement standard.

6
Using Variables

• // Program 2 Using a Variable
• include
• main()
• int value // value is a variable of type int
• value 1023 // assigns 1023 to value
• printf("This program prints the value ")
• printf("d\n", value)
• return 0

7
Using Variables

• // This program does conversion of gallons to
  liters
• include
• int main()
• int gallons, liters // two variables of type
  int
• printf("Enter number of gallons ")
• scanf("d", gallons) // console input
• liters gallons 4 // convert to liters
• printf("Liters d" , liters)
• return 0
• // IS THIS VERY ACCURATE??

8
Using Variables

• // This program does conversion of gallons to
  liters
• include
• int main()
• float gallons, liters // two variables of type
  float
• printf("Enter number of gallons ")
• scanf("f", gallons) // console input
• liters gallons 3.7854 // convert to liters
• printf("Liters f" , liters)
• return 0
• // Much more accurate

9
Classroom Project

• Problem 3, p. 30

10
Classroom Project

• We have an urgent need for a computer program
  which will calculate the area of a square
• Your program should prompt for the base b and
  height h as input then it will calculate and
  print out the area.

h
b
11
Review

• All programs have a main() function, and that is
  where program execution begins
• All variables must be declared before they are
  used
• C supports a variety of data types, including
  integer and floating point
• For output use printf() statement
• For input use scanf() statement
• Program execution stops when the end of main() is
  reached (or return 0)