Computer Generations Overview

First Generation Computers

• Achieved a processing speed of 5000 additions per second.
• Utilized machine language for programming.
• Depended heavily on vacuum tubes, which were prone to generating heat and consuming large power.
• Notable drawbacks included their large size and expense.
• Examples include ENIAC, EDVAC, IBM-701, and IBM-650.

Second Generation Computers

• Operated from 1956 to 1963 and introduced transistors, a 1947 invention from Bell Labs.
• Transistors provided cost-efficiency, reduced power usage, compact size, reliability, and speed improvements over vacuum tubes.
• Employed magnetic cores for primary memory and magnetic tape/disks for secondary storage.
• Advantages included reduced size, increased speed, and the ability to save instructions in memory.
• Programming utilized machine and assembly languages like COBOL and FORTRAN.
• Air conditioning was necessary due to heat, and they were mainly for commercial use.
• Examples included IBM 7049 Series and CDC 3600.

Third Generation Computers

• Spanned from 1964 to 1971, characterized by integrated circuits (ICs) comprising numerous transistors on a silicon chip.
• Offered increased speed, reduced size, greater reliability, and less heat generation.
• Integrated circuits allowed interaction with I/O devices and were often accompanied by operating systems.
• Examples include IBM System/360 and PDP-8.

Fourth Generation Computers

• Marked by the introduction of microprocessors in the early 1970s, with over 100,000 transistors on a single chip.
• Intel's 4004, an early four-bit microprocessor, led the way for subsequent models like 8008 and 8086.
• Notable features included VLSI technology, portability, high speed, and significant accuracy and reliability.
• Compatible with large memory interfacing.
• Examples included a series of Intel processors and AMD processors.

Fifth Generation Computers

• Focused on artificial intelligence applications post-1988, featuring ULSI microprocessors and nano-meter technology.
• Employed high-level languages such as C, C++, Java, and .NET.
• Noted for faster processing, decreased costs, intelligent capabilities, and parallel processing.
• Examples comprised desktops, laptops, and Chromebooks.

Computer Memory

• Primary memory includes cache and is categorized as temporary or permanent storage.
• RAM (temporary storage, lost when powered off) and ROM (non-volatile, contains essential programs).
• Cache memory is smaller and faster, storing frequently accessed programs.
• Secondary storage (e.g., hard drives, DVDs) is slower but offers permanent and larger capacity for data.

CPU and Control Units

• The CPU performs arithmetic and logic operations and executes instructions from memory.
• Two primary control unit architectures: hardwired (faster but more complex) and microprogrammed (more flexible).
• Different types of registers exist, including general-purpose and specialized registers like IR, PC, MAR, and MDR.

Instruction Execution Process

• The program execution involves fetching, decoding, reading operands (if necessary), executing operations, and writing back results.

Performance Metrics

• MIPS (Million Instructions Per Second) measures execution rate, inversely related to execution time.
• Performance is defined as 1 divided by execution time.

Architecture Classification

• Distinctions between CISC and RISC architectures based on instruction complexity and handling.
• Execution time affects perceived performance, specifically through response time and throughput.

Memory Addressing

• Memory addressing involves understanding big-endian (most significant byte at lowest address) and little-endian (least significant byte at lowest address) formats for data storage.

Example: Instruction Comparison

• CISC: Directly operate on memory banks with complex instructions and addressing modes.
• RISC: Focus on registers with simpler instructions emphasizing hardware efficiency.