Computer Science 1026A/B Lecture Notes - Lecture 2: Microsoft Word, Hypotenuse, Arithmetic Logic Unit
1 Jul 2018
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Chapter 1: A SHORT INTRODUCTION TO HARDWARE,
SOFTWARE, AND ALGORITHM DEVELOPMENT
Goals
●About computer hardware, software and programming
●How to write and execute your first Python program
●How to diagnose and fix programming errors
●How to use pseudocode to describe an algorithm
Computer Programs
●A computer program tells a computer the sequence of steps needed to complete
a specific task
○The program consists of a very large number of primitive (simple)
instructions
●Computers can carry out a wide range of tasks because they can execute
different programs
○Each program is designed to direct the computer to work on a specific
task
Programming:
●The act of designing, implementing, and testing computer programs
Hardware and Software
●Hardware consists of the physical elements in a computer system
○Some very visible examples are the monitor, the mouse, external storage,
and the keyboard.
●The central processing unit (CPU) performs program control and data
processing
●Storage devices include memory (RAM) and secondary storage
○Hard disk
○Flash drives
○CD/DVD drives
●Input / output devices allow the user to interact with the computer
○Mouse, keyboard, printer, screen…
Computer’s Components
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The CPU
●The CPU has two components, the control unit and the arithmetic logic unit
●The control unit directs operation of the processor
○All computer resources are managed by the control unit.
○It controls communication and co ordination between input/output devices.‐
○It reads and interprets instructions and determines the sequence for
processing the data.
○It provides timing and control signals
●The arithmetic logic unit contains the circuitry to perform calculations and do
comparisons.
○It is the workhorse portion of the computer and its job is to do precisely
what the control unit tells it to do.
Storage
●There are two types of storage:
○Primary Storage
○Secondary Storage
●Primary storage is composed of memory chips: electronic circuits that can store
data as long as it is provided electric power
●Secondary storage provides a slower, less expensive storage that is persistent:
the data persists without electric power
●Computers store both data and programs
○The data and program are located in secondary storage and loaded into
memory when the program is executed
Memory
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●A simple way to envision primary memory is a table of cells all the same size,
one byte, and each containing a unique address beginning with 0.
○The “typical” computer has a main memory ranging from 4 gigabytes (GB),
to 32 GB.
●How big is a gigabyte?
○A byte is 8 bits.
○A kilobyte, KB, is 1024 bytes, or “about 1 thousand bytes.”
○A megabyte, MB, is 1,048,576 bytes, or “about 1 million bytes.”
○A gigabyte, GB, is 1,073,741,824 bytes or “about 1 billion bytes.”
Executing a Program
●Program instructions and data (such as text, numbers, audio, or video) are stored
in digital format
●When a program is started, it is brought into memory, where the CPU can read it.
●The CPU runs the program one instruction at a time.
○The program may react to user input.
●The instructions and user input guide the program execution
○The CPU reads data (including user input), modifies it, and writes it back
to memory, the screen, or secondary storage.
Software
●Software is typically realized as an application program
○Microsoft Word is an example of software
○Computer Games are software
○Operating systems and device drivers are also software
●Software
○Software is a sequence of instructions and decisions implemented in
some language and translated to a form that can be executed or run on
the computer.
●Computers execute very basic instructions in rapid succession
○The basic instructions can be grouped together to perform complex tasks
●Programming is the act of designing and implementing computer programs
Algorithms
Introduction to Algorithms
●If you want a computer to perform a task, you start by writing an algorithm
●An Algorithm is:
○a sequence (the order mattering) of actions to take to accomplish the
given task (Solve problems or class of problems)
○An algorithm is like a recipe; it is a set of instructions written in a sequence
that achieves a goal
●For complex problems software developers write an algorithm before they
attempt to write a computer program
●For this class we will ALWAYS write an algorithm for each project
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COMPSCI 1026A/B Full Course Notes
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Document Summary
How to write and execute your first python program. How to diagnose and fix programming errors. How to use pseudocode to describe an algorithm. A computer program tells a computer the sequence of steps needed to complete a specific task. The program consists of a very large number of primitive (simple) instructions. Computers can carry out a wide range of tasks because they can execute different programs. Each program is designed to direct the computer to work on a specific task. The act of designing, implementing, and testing computer programs. Hardware consists of the physical elements in a computer system. Some very visible examples are the monitor, the mouse, external storage, and the keyboard. The central processing unit (cpu) performs program control and data processing. Storage devices include memory (ram) and secondary storage. Input / output devices allow the user to interact with the computer. The cpu has two components, the control unit and the arithmetic logic unit.
