Computer Software - Introduction to Computing - Lecture Slides, Slides of Introduction to Computing

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CS101 Introduction to Computing

Lecture 10

Computer Software

Lecture 8 was on the binary number

system and logic operations

1. About the binary number system, and how it differs from the decimal system
2. Positional notation for representing binary and decimal numbers
3. A process (or algorithm) which can be used to convert decimal numbers to binary numbers
4. Basic logic operations for Boolean variables, i.e. NOT, OR, AND, XOR, NOR, NAND, XNOR
5. Construction of truth tables (How many rows?)

We mentioned in Lecture 4 that at the

highest level, two things are required for

computing

Hardware: The physical equipment in a computing

environment such as the computer and its

peripheral devices (printers, speakers...)

Software: The set of instructions that operates various

parts of the hardware. Also termed as “computer

program”

Computer Software

• The HW needs SW to be useful; the SW needs HW

to be useful

• When the user needs something done by the

computer, he/she gives instructions in the form of

SW to computer HW

• These instructions need to be written in a language

that is readily understood by computer uP

Language Translators

• Human programmers write programs in a language

that is easy to understand for them

• They use language translators to convert that

program into machine language – a language that is

easy to understand for the uPs

• We’ll have more to say about the machine language

and language translators in a future lecture

Software Development

• Writing very short programs is easy, but developing reasonably-sized programs is quite difficult as you are going to learn over the next few years
• The SW development process involves many steps, and coding, that is typing the instructions in a high-level language is only a small part of that process – taking-up only around 15% of the effort
• A summary of the steps involved is shown on the screen. We’ll have more to say about them during the 20 th^ lecture

Two Major Types of SW

• System SW
  • Programs that generally perform the background tasks in a computer. These programs, many times, talk directly to the HW
• Application SW
  • Programs that generally interact with the user to perform work that is useful to the user. These programs generally talk to the HW through the assistance of system SW
• The diagram on the screen shows the relationship

between HW and these two types of SW

Hardware

Operating System

Utility LanguageTranslator

Device Driver

Scientific Apps.

Business Apps.

Productivity Apps.

Entertainment Apps.

System software

Application software

Operating System

• Performs its work invisibly to control the internal functions of a computer, e.g. maintaining files on the disk drive, managing the screen, controlling which tasks the uP performs and in what order
• It interacts directly with the computer HW
• Other SW normally does not directly interact with the HW, but through the OS
• Examples:

Windows Mac OS Linux Unix Solaris DOS CP/M VMS Docsity.com

Firmware

• OS components that are stored permanently on

chip (ROM) and not on the disk drive

• When a computer is powered-on, firmware is the

first program that it always executes

• Firmware consists of startup and a few low-level

I/O routines that assist the computer in finding

out and executing the rest of the OS

• On IBM-compatible PC’s, it is called BIOS

Language Translators

Programs that take code written in a HLL and translate it

into a low-level language that is easily understood by the uP

1. Compiler translates the program written in a HLL in one

go. The translated code is then used by the uP whenever

the program needs to be run

2. Interpreter translates the HLL program one statement at

time. It reads a single statement, translates it into machine

language and passes that machine language code to the uP

and then translates the next statement, and so on …

Device Drivers

• A computer program that facilitates the

communication between the computer and a

peripheral device (e.g. printer, mouse, etc.)

• It takes the instructions and/or data from the

computer and converts them into a form that is

readily understood by a peripheral device, and vice

versa

Hardware

Operating System

Utility LanguageTranslator

Device Driver

Scientific Apps.

Business Apps.

Productivity Apps.

Entertainment Apps.

System software

Application software

Another way of classifying SW

• Shrink-Wrapped SW
  • You can just go to a shop and buy it
• Custom-built SW
  • You cannot just go to a shop and buy it; you have to find someone who can develop it for you