The document discusses the main components and concepts of computer organization. It summarizes that a digital computer contains four main blocks: the central processing unit (CPU), memory, input, and output. The CPU executes programs stored in memory and communicates with other components via address, data, and control buses. A microprocessor is a CPU on a single chip, while a microcontroller contains a CPU as well as peripherals like timers on one chip. The document also defines basic units of digital information like bits, bytes, and word length, and explains concepts like address space and Von Neumann's stored program concept.

1. General Aspects of Computer Organization
(Lecture-1)
R S Ananda Murthy
Associate Professor
Department of Electrical & Electronics Engineering,
Sri Jayachamarajendra College of Engineering,
Mysore 570 006
R S Ananda Murthy General Aspects of Computer Organization

2. Specific Learning Outcomes
After completing this lecture the student should be able to –
List the four main blocks in a digital computer.
Explain the meaning of address bus, data bus and control
bus in a digital computer.
List the differences between a microprocessor and a
microcontroller.
Explain the meaning of bit, nibble, byte and word length of
a microcontroller or a microprocessor.
Explain how the word length of a processor affects its
performance.
Explain the meaning of address space.
Explain the Stored Program Concept of Von Neuman.
R S Ananda Murthy General Aspects of Computer Organization

3. Functional Units in a Digital Computer
CPUInput Output
Memory
External
World
External
World
Arrows indicate direction of information flow.
Central Processing Unit (CPU) executes the program
stored in memory.
Typical devices in input block: keyboard, mouse.
Typical devices in output block: monitor, speaker, printer.
R S Ananda Murthy General Aspects of Computer Organization

4. Address, Data and Control Buses in Computer
Memory
CPU
Input
Output
Address Bus
Data Bus
Control Bus
Real
World
A set of parallel wires is called a bus.
Address is output by the CPU on the address bus.
Data is transmitted between the CPU and other devices
over the data bus.
Control signals are transmitted over the control bus.
R S Ananda Murthy General Aspects of Computer Organization

5. Microprocessor – CPU on a Chip
Arithmetic Logic
Unit (ALU)
Register ArrayControl
Unit (CU)
Central Processing Unit (CPU)
CU generates signals required to fetch instructions from
the memory and execute them.
ALU performs arithmetic and logical operations.
Register array has registers to store data temporarily.
Microprocessor is a CPU on a single chip.
R S Ananda Murthy General Aspects of Computer Organization

6. Microcontroller – CPU and Peripherals on a Chip
CPU R/WM ROM
I/O
Ports
Timer/
Counter
Serial
COM
Port
Microcontroller
Some modern microcontrollers even have on-chip
Analog-to-Digital Converter (ADC) and Digital-to-Analog
Converter (DAC).
R S Ananda Murthy General Aspects of Computer Organization

7. Bit, Nibble, Byte and Word Length of CPU
A binary digit is known as bit. It can be 0 or 1.
In modern digital computers all instructions and data are
represented using bits.
A group of four bits is a nibble. Eg. 1101, 1010.
A group of eight bits is a byte. Eg. 11011010, 10101010.
The data bus width is known as word length of CPU. For
eg. ATmega328 MCU has a word length of 1-byte because
its data bus width is 8-bits.
A CPU with longer word length is faster because it can
process more bits in one operation.
R S Ananda Murthy General Aspects of Computer Organization

8. No. of Bits in Address and Address Space
MemoryAdr. Hex
0000H
FFFFH
0001H
Starting
Ending
.
.
.
.
.
.
.
65536 Locations
0000 0000 0000 0000B
Address in Binary
1111 1111 1111 1111B
.
.
.
.
.
.
.
.
.
.
.
.
.
.
0000 0000 0000 0001B
With N bits in the address, CPU can access 2N locations.
Eg. if there are 16-bits in the address as shown above,
then, the address space has 216 = 65536 locations.
R S Ananda Murthy General Aspects of Computer Organization

9. Von Neumann’s Stored Program Concept
Address Memory
0000 Byte
0001 Byte
0002 Byte
0003 Byte
0020
.
.
.
CPU
0002
PC
Halt
Content of
a memory
location
0021
Program Counter (PC) – also known as Location Counter –
in side the CPU points to the next instruction in the
memory to be fetched and executed.
PC stops incrementing when HALT instruction is
recognized by the CPU.
R S Ananda Murthy General Aspects of Computer Organization

10. License
This work is licensed under a
Creative Commons Attribution 4.0 International License.
R S Ananda Murthy General Aspects of Computer Organization