Computer Engineering & Management Notes

Hybrid computer

Analog computer

Networking and the Internet

Block diagram of computer

1. CENTRAL PROCESSING UNIT (CPU):

• CPU is the brain of a computer.
• Transform raw data into useful information.
• CPU is responsible for all Processing.
• It has two parts

• It is the part where actual processing takes place.
• It can perform Addition, Subtraction, Multiplication, Division, Square Roots (etc) and logic operations such as AND, OR (etc) on binary numbers.

• It tells the computer that, “What specific sequence of operations it must perform”.
• It also specifies timing of the instructions.
• Its function is to Fetch, Decode and Execute instructions that are stored in memory.
• It controls

• Arithmetic Logic Unit
• All Input/Output Devices

• Also called Primary memory or Internal memory.
• Memory is used to store data temporary or permanently.
• Data stored in memory can be used for required task.
• RAM and ROM are most commonly used as main memory

Hardware

History of computing hardware

Logic gate

Type	Distinctive shape (IEEE Std 91/91a-1991)	Rectangular shape (IEEE Std 91/91a-1991 IEC 60617-12 : 1997)	Boolean algebra between A & B	Truth table
Inverter
NOT			${\displaystyle {\overline {A}}{\text{ or }}{\sim }A}$	INPUT OUTPUT A NOT A 0 1 1 0
2-input gates
AND			${\displaystyle A\cdot B{\text{ or }}A\;\&\;B}$	INPUT OUTPUT A B A AND B 0 0 0 0 1 0 1 0 0 1 1 1
OR			${\displaystyle A+B}$	INPUT OUTPUT A B A OR B 0 0 0 0 1 1 1 0 1 1 1 1
XOR			${\displaystyle A\oplus B}$	INPUT OUTPUT A B A XOR B 0 0 0 0 1 1 1 0 1 1 1 0
Inverted 2-input gates
NAND			${\displaystyle {\overline {A\cdot B}}{\text{ or }}A\uparrow B}$	INPUT OUTPUT A B A NAND B 0 0 1 0 1 1 1 0 1 1 1 0
NOR			${\displaystyle {\overline {A+B}}{\text{ or }}A-B}$	INPUT OUTPUT A B A NOR B 0 0 1 0 1 0 1 0 0 1 1 0
XNOR			${\displaystyle {\overline {A\oplus B}}{\text{ or }}{A\odot B}}$	INPUT OUTPUT A B A XNOR B 0 0 1 0 1 0 1 0 0 1 1 1

Web server

Programming language

expression ::= atom | list
atom       ::= number | symbol
number     ::= [+-]?['0'-'9']+
symbol     ::= ['A'-'Z''a'-'z'].*
list       ::= '(' expression* ')'

Logic programming

H :- B₁, …, B_n.

to show/solve H, show/solve B₁ and … and B_n

B₁ and … and B_n implies H.

Functional programming

• Procedures correspond to functions. Both allow the reuse of the same code in various parts of the programs, and at various points of its execution.
• By the same token, procedure calls correspond to function application.
• Functions and their invocations are modularly separated from each other in the same manner, by the use of function arguments, return values and variable scopes.

• Whereas procedural languages model execution of the program as a sequence of imperative commands that may implicitly alter shared state, functional programming languages model execution as the evaluation of complex expressions that only depend on each other in terms of arguments and return values. For this reason, functional programs can have a free order of code execution, and the languages may offer little control over the order in which various parts of the program are executed. (For example, the arguments to a procedure invocation in Scheme are executed in an arbitrary order.)
• Functional programming languages support (and heavily use) first-class functions, anonymous functions and closures, although these concepts are being included in newer procedural languages.
• Functional programming languages tend to rely on tail call optimization and higher-order functions instead of imperative looping constructs.

Object-oriented programming

Procedural programming

OOP in a network protocol

• Fields defining the data values that form messages, such as their length, codepoint and data values.
• Objects and collections of objects similar to what would be found in a Smalltalk program for messages and parameters.
• Managers similar to AS/400 objects, such as a directory to files and files consisting of metadata and records. Managers conceptually provide memory and processing resources for their contained objects.
• A client or server consisting of all the managers necessary to implement a full processing environment, supporting such aspects as directory services, security and concurrency control.

Polymorphism

Composition, inheritance, and delegation

Objects and classes

• Classes – the definitions for the data format and available procedures for a given type or class of object; may also contain data and procedures (known as class methods) themselves, i.e. classes contains the data members and member functions
• Objects – instances of classes

• Class variables – belong to the class as a whole; there is only one copy of each one
• Instance variables or attributes – data that belongs to individual objects; every object has its own copy of each one
• Member variables – refers to both the class and instance variables that are defined by a particular class
• Class methods – belong to the class as a whole and have access only to class variables and inputs from the procedure call
• Instance methods – belong to individual objects, and have access to instance variables for the specific object they are called on, inputs, and class variables

Object-oriented programming (OOP)

Parallel array

int  ages[]   = {0,          17,        2,          52,         25};
char *names[] = {"None",     "Mike",    "Billy",    "Tom",      "Stan"};
int  parent[] = {0 /*None*/, 3 /*Tom*/, 1 /*Mike*/, 0 /*None*/, 3 /*Tom*/};

for(i = 1; i <= 4; i++) {
    printf("Name: %s, Age: %d, Parent: %s \n",
           names[i], ages[i], names[parent[i]]);
}

my %data = (
    first_name   => ['Joe',  'Bob',  'Frank',  'Hans'    ],
    last_name    => ['Smith','Seger','Sinatra','Schultze'],
    height_in_cm => [169,     158,    201,      199      ]);

for $i (0..$#{$data{first_name}}) {
    printf "Name: %s %s\n", $data{first_name}[$i], $data{last_name}[$i];
    printf "Height in CM: %i\n", $data{height_in_cm}[$i];
}

first_names   = ['Joe',  'Bob',  'Frank',  'Hans'    ]
last_names    = ['Smith','Seger','Sinatra','Schultze']
heights_in_cm = [169,     158,    201,      199      ]

for i in range(len(first_names)):
    print "Name: %s %s" % (first_names[i], last_names[i])
    print "Height in CM: %s" % heights_in_cm[i]

# Using zip:
for first_name, last_name, height in zip(first_names, last_names, heights_in_cm):
    print "Name: %s %s" % (first_name, last_name)
    print "Height in CM: %s" % height_in_cm