Computers, Software, and Data

Tom Kelliher, CS 102

Jan. 30, 2004

Administrivia

Announcements

How do I switch printers in the Lab?

Assignment

Read 1.6--10.

Know the ``Things to Remember'' and ``Important Concepts'' material on pp. 37 and 38.

Be able to answer these questions from pp. 39--42: 1, 2, 4, 7, 11, 12, 21, 25, 28, and 31.

From Last Time

Syllabus, survey.

Outline

  1. Computers, Software, and Data.

Coming Up

Inside a computer.

What's a Computer?

A block diagram:

  1. What is memory? How does it differ from storage?

  2. What parts of a PC are considered input devices? Output devices? Both?

How is Software Run?

Consider the following simple program:

 1:   let sum = 0
 2:   print "How many numbers? "
 3:   read count
 4:   let loopCount = count
 5:   if loopCount equals 0 goto 11
 6:   print "Next number: "
 7:   read input
 8:   let sum = sum + input
 9:   let loopCount = loopCount - 1
10:   goto 5
11:   let average = sum / count
12:   print "The average is:", average, "."
13:   end
  1. Where do we begin?

  2. After completing one step, where do we proceed?

  3. Operations: assignment, arithmetic, decision, branch, I/O.

  4. Operands: Variables, constants (numeric and string).

How is Data Kept?

  1. Computers use the binary system. Why?

  2. Binary digits.

    Conversion between binary and decimal is fairly simple, but tedious --- write/use a program.

  3. Bits, bytes, words.

  4. Memory locations: cells with addresses.

  5. How do we represent characters? ASCII code:
    1. A: 01000001

    2. 4: 00110100

  6. How does the computer know if a memory location contains numbers, characters, variables, or instructions?



Thomas P. Kelliher
Thu Jan 29 19:22:27 EST 2004
Tom Kelliher