Class 10: Basic Input and Output in C

Held: Tuesday, 8 February 2011

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

Related Pages:

• EBoard.
• Lab: Input and Output.
• Reading: K&R 7.1-7.2, 7.4.

Notes:

• No reading due tonight!
• I have a sick child at home, so I will not have office hours today.
• Assignment 3 remains due tomorrow night.
• Exam 1 to be distributed on Wednesday.
• EC: Saturday's basketball games.
• EC: Sunday nights FreeNet.

Overview:

• I/O Basics.
• 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.

Lab

• Do the lab.
• Be prepared to reflect.