Transcript 99_Introduction

Chapter 1
Computers, Compilers, & Unix
Overview
 Computer
hardware
 Unix
 Computer
 Compilers
Languages
Computer Hardware
 Central
Processing Unit (CPU)
 The
heart and brains of a computer
 The device that performs all calculations and data
manipulation in a computer
 Main
 The
Memory (RAM)
place the CPU looks for instructions and data to
process
Computer Hardware
 Mass
Storage (hard drive)
 Holds
information not immediately needed by CPU
 Holds massive amounts of data
 Input/Output
 keyboard,
Devices
mouse, monitor, printer
 Devices used to move information into and out of the
computer
Basic Architecture
 Processor
(CPU)
 Main Memory
CPU
Memory
 volatile
 I/O
devices
 secondary
memory
 communications
 terminals
 System
a
System Bus
Disk
Network
Controller Controller
Serial Device
Controller
interconnection
bus is used to exchange data and control information
What is an operating system?
 Acts
as interface between computer system
resources (hardware) and applications
 Manages
the way other programs use system
resources and communicate with each other
 Common
operating systems
 Windows
 In
XP, Macintosh OS, & Linux
CS 201 we use Solaris, a type of Unix
Unix file system
 Home
directory
A directory set aside for your personal use
 The starting point when you log in

 Working

directory
Whatever directory you are currently in

 The
Initially, the working directory is the home directory
cd command is used to change the working directory
cd .. Moves up one level in the directory structure
 cd <directory> moves down one level, into the given directory

 The
pwd command gives the full path of the working
directory
 The ls command lists the contents of the working directory
Programming Languages
 Common
programming languages include …
C C++ Java Pascal Visual Basic
COBOL Lisp Scheme Ada
 These
FORTRAN
high-level languages
Resemble human languages
 Are designed to be easy to read and write
 Use more complicated instructions than the CPU can follow
 Must be translated to zeros and ones for the CPU to execute a
program

Low-level Languages
 An
assembly language command such as
ADD X Y Z
might mean add the values found at x and y
in memory, and store the result in location z.
 Assembly
language must be translated to
machine language (zeros and ones)
0110 1001 1010 1011
 The CPU can execute machine language instructions
Compilers
 Translate
high-level language to
machine language
 Source

the original program in a high level language
 Object

code
code
the translated version in machine language
Linkers
 Some
programs we use are already compiled
 Their
object code is available for us to use
 Input
and output routines
 A Linker
 The
combines
object code for the programs we write
and
 The object code for the pre-compiled routines
into
The machine language program the CPU can run
From Source Code to Executable Program
#include <iostream>
using namespace std;
int main()
{
cout << "Hello
World!" << endl;
return 0;
}
compiler
1001010100010
1010010101001
0010101001010
0101001001001
0100101010101
0010010100100
1001010010100
1010000100100
1001
library
linker
0100101010010
1001010010010
0101001010101
0100100101001
0010010100101
0010100101010
1010100100100
1000100100100
1001
executable
file
1001010100010
1010010101001
0010101001010
0101001001001
0100101010101
0010010100100
1001010010100
1010000100100
1001
object file
Programming & Problem Solving
 Algorithm
 A sequence
of precise instructions which
leads to a solution
 Program
 An
algorithm expressed in a language the computer
can understand
Program Design
 Programming
 No
is a creative process
complete set of rules for creating a program
 Design
process for CS-201
 Problem
Solving Phase
 Produce
an algorithm that solves the problem
 Implementation
 Translate
& Testing Phase
into a valid, functioning program
Problem Solving Phase
 Be
certain the task is completely specified
 What
is the input?
 What information is in the output?
 How is the output organized?
 Develop
the algorithm before implementation
 Experience
shows this saves time in getting your
program to run
 Test the algorithm for correctness
Implementation & Testing Phase
 Translate

Easier as you gain experience with the language
 Compile

the source code
The compiler identifies violations of the programming language's
grammar

 Run

the algorithm into a programming language
These are known as syntax errors
the program on sample data
Verify correctness of results
If you made mistakes in your algorithm design, or in your translation to the
programming language, you'll see errors
 These are known as logic errors

 Modify
the algorithm and/or program and repeat