Computers, Software, and Data

Tom Kelliher, CS 102

Sept. 5, 2001

Administrivia

Announcements

How do I switch printers in the Lab?

How are network accounts coming along?

Assignment

Read the following and be able to answer the questions.

1. How Hard Disks Work
   (http://www.howstuffworks.com/hard-disk.htm) Read the entire article.

   At the most basic level, where is information stored on a hard disk? What is a platter? Does a hard disk usually have more than one? What is a sector? A track?

2. How Computer Memory Works
   (http://www.howstuffworks.com/computer-memory.htm) Read the first two pages.

   Name two types of temporary storage. Two types of permanent storage. What is ROM? When an application is loaded or a document opened, where does it go? Why?

3. How Does a Bubble Jet Printer Work?
   (http://www.howstuffworks.com/question163.htm)

   How does a bubble jet printer form an ink droplet? How many nozzles will it have? Can they all form droplets simultaneously?

From Last Time

Syllabus, survey.

Outline

1. Survey results.

2. 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?