1. Introduction to Computers and Programming
Hardware
Software
Computer languages
Compiling, interpreting and assembling

2. Computer Basics
A computer system consists of both hardware and software.
Hardware - the physical components
Software - the instructions, or rather, computer programs, that tell the hardware what to do

3. Common Hardware Components
Memory
Processor
(CPU)
Input Devices
(such as mouse and keyboard)
Output Devices
(such as video display or printer)
Processor:
Central Processing Unit (CPU)
interprets and executes program instructions
Memory:
volatile and non-volatile
holds data and instructions
Input devices:
keyboard, mouse, touch-screen
game controllers
sensors
Output device(s)
video display, printer
robotic devices

4. Classification of Memory
At a high-level there are two types of memory:
Volatile – contents are lost when power is turned off:
Main memory (stores programs and data during execution)
Cache memory
Fastest and most expensive form of memory, per byte
Non-Volatile – contents are maintained when power is turned off:
Hard drive (internal or external, stores programs and data permanently)
CD, DVD
Flash drive, floppy disk
Tape (still used extensively)
Slowest and cheapest form of memory, per byte

5. Memory Organization Bit = one binary digit, either 0 or 1
Byte = 8 bits
Word = machine dependant, typically 4 bytes
Larger groupings: (number of bytes)
name approximation exact
Kilobyte (KB) 2^ ^3
Megabyte (MB) 2^ ^6
Gigabyte (GB) 2^ ^9
Terabytes (TB) 2^ ^12
Petabyte (PB) 2^ ^15
Exabyte (EB) 2^ ^18
Zetabyte (ZB) 2^ ^21
Yottabyte (YB) 2^ ^24

6. Binary Encodings
Everything in memory is “encoded” in binary, i.e., as a sequence of bits.
“A” =>
45 =>
“DOG” =>
Generally, the encoding of an object is unique among all similar objects, e.g., the encoding of “A” is different from the encoding of “B.”
How many binary sequences are there on n bits?
How many bits are needed to uniquely encode k items?

7. Main Memory Organization
A list of locations, each containing one byte of data.
Each location has an associated “number,” which is commonly referred to as its’ address.
Is said to be byte addressable.
Also called Random Access Memory (RAM).
The number of bytes per data item may vary from one item to another, and from one computer system to another.
Integer => 4 bytes (1 word)
Character => 1 or 2 bytes

8. Running (Executing) a Program
A (computer) program is a set of instructions for a computer to follow, or rather, execute.
The term application is sometimes used to informally refer to a computer program (we will use the term more formally later).
Program
Computer
Data
(input for the program)
Output

9. Many Types of Programs
System Software - Part of the computers “infrastructure,” and necessary for the system to operate:
Operating Systems - DOS, Microsoft Windows, MacOS, Linux, UNIX, etc.
Database Systems – Oracle, IBM DB2, SQL Server, Access
Networking Software
Web Servers
Application Servers
User Applications - Not required for the system to operate:
Games
Office Applications – Word, Powerpoint, Excel
Web Browsers
Text Editors – textedit, vi, emacs, notepad

10. Various Types of User Interfaces
Graphical User Interface (GUI)
Windows, menus, buttons, sliders, etc.
MacOS, Windows
Sometimes also called “event-driven” interfaces
First developed by Xerox Corporation
Command-Line:
User types in commands one line at a time
DOS (Start -> run -> cmd)
Unix xterm
Application Program Interface (API)
Allows one program to communication, interact or “interface” with another, or with some external, physical device.
ODBC, JDBC, Swing, AWT

11. Programming Language Hierarchy
Programs are written, or coded, in a programming language.
There are many different types of programming languages.
Machine Language
Assembly Language
High-Level Language

12. High-Level Languages High-Level Language (HLL):
Java, C, C++, C#, COBOL, FORTRAN, BASIC, Lisp, Ada, etc.
closest to natural language
words, numbers, and math symbols
multi-line statements/commands
relatively easy for people to read (it’s for people)
not directly understood by hardware
“portable” (hardware independent)
A program in a HLL is frequently referred to as:
a source program
source code
source file
source

13. High-Level Language Example (Java)
public class SimpleProgram {
public static void main(String[] args)
System.out.println(“Hello out there.”);
System.out.println(“I will add two numbers for you.”);
int x;
double d;
x = 3752;
d = ;
System.out.println(“The sum of ” + x + “ and ” + d + “ is:”);
System.out.println(x + d); }

14. Machine Languages Machine Language (lowest level):
just 0s and 1s
single-line commands
very difficult for humans to read
directly understood by hardware
not portable (hardware dependent)
A program in machine language is frequently referred to as:
an object program
object code
executable program
executable code
executable

15. Machine Language Example
000000
000001
000010
000110
100000
100011
000011
001000
000100 :

16. Assembly Languages Assembly Language:
a more readable version of machine language (also for people)
words, abbreviations, letters and numbers replace 0s and 1s
single-line statements/commands
easily translated to machine executable code
like machine code, not portable (hardware dependent)
So, if we already have HLLs for people, why do we need assembly language?
compilation results in a loss of meaning…sort of
control over the resulting machine code

17. Assembly Language Example
PUSH DX
MOV AH 08
INT 21
CMP AL 30
JB 0203
CMP AL 46
JA 0203
CMP AL 39
JA 021B
MOV AH 02
MOV DL AL
SUB AL 30
POP DX
RET
CMP AL 41
SUB AL 37

18. Getting from Source to Machine Code
Translating a program in a high-level language to machine code is called compiling.
A program that compiles programs is called a compiler.
A program that translates an assembly language program into machine code is called an assembler.
Compilers and assemblers need to know the specific target hardware.
There is, however, one additional type of translation called interpreting…

19. Compilers vs. Assemblers vs. Interpreters
Compilers and Assemblers:
translation is a separate user step from execution
entire source program is translated before execution
sometimes said to be “off-line,” i.e. not at run time
Interpreters: (another way to translate source to object code)
translation is not a separate user step from execution
translation and execution occur “line at a time”
sometimes said to be “on-line,” i.e. at run time
The difference between compiling (or assembling) and interpreting a computer program, is analogous to the difference between translating a book, and interpreting a speaker.

20. Java Program Translation
Executing a java program involves both compilation and interpretation.
Java Program Translation & Execution:
Step #1: A java program is compiled; this produces a program in byte code.
Similar to assembly code, but hardware independent.
Step #2: An interpreter, called the Java Virtual Machine (JVM) translates the byte code program to hardware-specific machine code, and executes it.
Execution is done in an interpretive manner
Question:
Why not compile directly to machine code, rather than byte code?
Answer:
To make a long story short, portability over the internet.

21. Java Program Translation Including Linker
Oh, and, one other part of the translation process is linking…
Java Program
Previously Compiled Helper Programs
Java Compiler
Byte-Code
Program
Byte-Code Interpreter
Machine-Language
Instructions
Class Loader (i.e., Linker)
Computer Execution
of Machine-Language Instructions