Class 07: Basic Input and Output in C

Held: Tuesday, 7 September 2010

Summary: We consider in some detail input and output in C.

Related Pages:

• EBoard.
• Lab: Input and Output.
• Reading: K&R 7.1-7.4.

Notes:

• Are there questions on assignment 2?
• Note that the due date was changed until Thurday.
• I had a request to go a bit slower on how you compile, and I will do so.
• I expect to grade assignment 1 tonight.

Overview:

• I/O Basics.
• A Group Exercise.
• Lab!

The Basics

We typically print using printf

• The first parameter to printf is a format string that indicates how to present the remaining parameters.
  • Each part of the format string that begins with a % is an indication to insert the next of the remaining parameters.
• Kinds of format strings.
  • %d - an integer (decimal)
  • %5d - an integer, using at least 5 spaces
    • You can substitute numbers
  • %f - a double
  • %.2f - a double, with two decimal places after the decmial
  • %s - a string

We typically read using scanf

• The first parameter to scanf is also a format string.
• The remaining parameters are the variables into which we want to read values.
• We prefix each variable with an ampersand, &
• For example,

    scanf ("%d", &i);
  

• We can also specify a maximum number of characters to read, as in

    scanf("%1d%1d%1d", &x1, &x2, &x3);
  

We can also read using getchar and write using putchar.

Group Exercise

• Let's write a program that converts quarts to liters.
• Note that there are approximately 1.056710 quarts per liter.

Lab

• Do the lab.
• Be prepared to reflect.