Transcript Topic 1: Introduction to Computers and Programming

Topic 1: Introduction to
Computers and Programming
“A journey of a thousand miles must begin
with a single step.” - Lao Tzu
Introduction to Computer
Organization
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Computers are composed of two
distinct components:
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Hardware – the equipment used to
perform computations. This includes the
CPU, memory, hard disk, etc…
Software – the programs that determine
the operations to be performed by the
hardware.
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Hardware Components
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Hardware consists of many types of
components:
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Primary Storage
Secondary Storage
The Central Processing Unit (CPU)
Input Devices
Output Devices
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Primary Storage and
Secondary Storage
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There are two primary types of storage
in a computer:
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Primary Storage – often referred to as
main memory, or just memory. This
storage is very quickly accessed by the
various hardware components.
Secondary Storage – includes such devices
as a hard disk, floppy disk, CD-ROM, DVDROM, etc…
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Memory Organization
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Computer memory is organized into
memory cells. Each cell has a unique
address, which allows the accessing of
each cell individually.
Programs are transferred from
secondary storage into primary storage
before they can be run.
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The Central Processing Unit
(CPU)
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The CPU is responsible for coordinating all
computer operations and performing the
operations specified in a program.
The CPU fetches an instruction from a
program loaded in memory, decodes the
instruction, retrieves necessary data,
performs the operation, and then saves the
result.
The CPU contains very high speed memory
cells termed registers, which holds the data
being operated on.
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Input and Output Devices
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Input devices are used to communicate
from some external source to the
computer. They include the keyboard
and the mouse.
Output devices are used to
communicate from the computer to
some external source. They include the
monitor and the printer.
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Computer Software
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All major computers run an operating
system.
An operating system is a special type of
program which controls the interaction
between all hardware components and
the user.
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Operating Systems Tasks
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Responsibilities of the OS include:
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Communicating with the user(s)
Managing resources including memory and
processor time among programs
Collecting data from input devices
Providing data to output devices
Accessing data from secondary storage
Writing data to secondary storage
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Binary Math
A binary digit or bit for short is the smallest unit of
computer information. Just as our familiar decimal
number system has 10 digits,(0,1,2,3,4,5,6,7,8,9) the
binary number system has only 2 digits (0,1). This is
the perfect number system for computers since we
can store a binary digit by making an electrical or
magnetic field either on or off, positive or negative, 1
or 0. In the decimal system we can count 10 (we
start counting with 0) items with one decimal place,
100 with two decimal places, 1000 with three decimal
places and so on.
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Binary Math
The binary number system works the same way except
since we only have 0s and1s our base is 2.
So we can count 2 permutations of 1 bit: 0 1
4 permutations of 2 bits: 00 01 10 11
8 permutations of 3 bits: 000 001 010 011 100 101 110
111
16 permutations of 4 bits: 0000 0001 0010 0011 0100
0101 0110 0111 1000 1001 1010 1011 1100 1101
1110 1111
...and so on.
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Binary Math
So in an eight bit byte, the numbers are represented this way:
Bit:
Value:
128 64
Example: 1
Values:
0
32
16
8
4
2
1
1
1
0
1
1
0
128 + 0 + 32 +16 + 0 + 4 + 2 + 0 = 182
The minimum number is 0 (all 0s) and the maximum number is
255 (all 1s), so you can represent 256 numbers (0-255) with
one byte.
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Computer Programming Machine Language
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Computer programs were originally written in
machine language. Machine language is a
sequence of binary numbers, each number
being an instruction.
Each instruction is computer-understandable.
00000000
00010101
00010110
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Computer Programming Assembly Language
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To make machine language more abstract,
assembly language was introduced.
Assembly language provides a one-to-one
mapping between a machine instruction and
a simple human-readable instruction.
CLR
ADD
ADD
A
A
B
00000000
00010101
00010110
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Computer Programming –
Assembly Language
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Assembly language is converted to computerunderstandable machine language by an
assembler.
Although assembly language is much more
clear and understandable than machine
language, it is still very difficult to program.
The assembly code for the sqrt() function in C
is composed of hundreds of assembly
instructions.
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Computer Programming –
High-Level Languages
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In order to get around these obstacles,
high-level languages were introduced.
High-level languages provide a one-tomany mapping between one high-level
statement and multiple assembly
language instructions.
High-level language is converted to
assembly instructions by a compiler.
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Computer Programming Compilation
A=6X3
MOV
MOV
LABEL1:
ADD
DEC
JNZ
STOR
EAX, 0
EBX, 3
// initialize EAX to 0
// set multiplicand
EAX, 6
EBX
LABEL1
A, EAX
//
//
//
//
multiplier
decrease count
loop if need to
store result in A
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Modern Software
Development
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Modern software development is done in
high-level languages, with few exceptions.
High-level language is first compiled from
source code to assembly and then assembler
into machine code. Modern compilers
perform the assembler function as well.
Compiled source code is called an object file.
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Modern Software
Development
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Programmers often use library functions,
which are pre-written functions provided as
part of the compiler/development toolset.
A library is an object file.
After the source code is compiled into
machine code, a linker resolves crossreferences among these object files, including
libraries. The object files are linked into an
executable file.
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Modern Software
Development
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The executable file can now be run.
The operating system loader loads the
executable file into memory and
schedules the program for execution.
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Modern Software
Development
Source Code File
Compiler
Object File
Other Object Files
(perhaps libraries)
Linker
Executable File
Loader
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The Software
Development Method
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Specify the problem.
Analyze the problem.
Design an algorithm to solve the
problem.
Implement the algorithm.
Test and verify the program.
Maintain and update the program.
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Review
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Name the principle components of a
computer.
What are three responsibilities of the
operating system?
What advantage does assembly language
have over machine language?
What advantages do high-level languages
have over assembly language?
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Review
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What computer program translates a source
code file into an object file?
What program combines object files and
produces an executable file?
What part of the operating system is
responsible for the loading and scheduling of
programs?
What are the steps in the software
development method?
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