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The third generation replaced discrete transistors with integrated circuits, which packed many components onto a single silicon chip. This made machines smaller, faster and more reliable than the transistor-based second generation. The first generation used vacuum tubes and the fourth used microprocessors.
The base of a number system is the count of distinct digit symbols it uses before a positional carry occurs. Decimal uses ten symbols, 0 through 9, so its radix is ten. Binary uses two, octal uses eight and hexadecimal uses sixteen.
Volatile memory needs a continuous power supply to hold data, and RAM is the standard example used in the Tamil Nadu syllabus. Switching off the computer clears the contents of RAM. ROM, hard disks and flash drives retain data without power.
Repeated division by two gives remainders 1, 0, 1, 1, which are read upwards to give 1101. Checking the place values: 8 + 4 + 0 + 1 equals 13. Hence 1101 is correct.
The Arithmetic Logic Unit, or ALU, carries out arithmetic operations and logical comparisons inside the processor. The control unit instead directs the sequence of operations. Hence the ALU is the part that actually computes.
System software manages the hardware and provides a platform for application programs, and the operating system is its main example. Spreadsheets, browsers and photo editors are application software written to do a user's specific task.
A byte is defined as a group of eight bits, and it is the standard unit for storing one character such as a letter or digit. Memory sizes are commonly quoted in bytes and its multiples. Four, sixteen and thirty-two bits are other word lengths, not a byte.
In hexadecimal, A stands for the decimal value ten. Evaluating place values gives 2 times 16 plus 10 times 1, which equals 32 plus 10, that is 42. So 2A in hexadecimal equals 42 in decimal.
Group the binary digits in threes from the right: 101 and 101. Each group 101 equals 5 in octal, so the result is 55. Grouping must always start at the rightmost bit.
Cache memory sits closest to the processor and holds frequently used instructions and data, so it is faster than main memory. Main and secondary memory are progressively slower. Virtual memory is a disk-based extension of RAM, not a physical fast store.
The AND gate outputs 1 only for the input combination 1,1 and outputs 0 for every other combination. This behaviour matches the truth table of logical multiplication. OR, NOT and NOR gates each behave differently.
To find the two's complement, first invert all bits to get 1010, then add 1 to obtain 1011. This representation is used to store negative numbers in binary. Adding 0101 and 1011 gives 10000, discarding the carry to leave zero, which confirms the result.
A mouse is a pointing input device that lets a user position a cursor and select items by clicking. Plotters, speakers and monitors all send results outward from the computer. Therefore only the mouse belongs to the input category.
Hexadecimal is base sixteen, so it needs sixteen symbols: the digits 0 to 9 supply ten and the letters A to F supply the remaining six. Binary uses only 0 and 1, octal uses 0 to 7, and decimal uses 0 to 9 with no letters.
Adding from the right: 1+0 gives 1, 1+1 gives 0 with a carry of 1, then 0+1+1 gives 0 with a carry of 1, and finally 1+0+1 gives 10. The result is therefore 10001, which equals 17 in decimal, matching 11 plus 6.
Four gigabytes equals 4 times 1024 megabytes, and each megabyte is 1024 times 1024 bytes. Multiplying gives 4,294,967,296 bytes, which is roughly 4.29 billion. This is why quoted capacity differs slightly from the decimal count.
The stored program concept, associated with von Neumann architecture, holds that program instructions reside in memory alongside data. The processor fetches and executes these instructions one after another. This allows a general-purpose machine to run different programs without rewiring.
A bit is a single binary digit, either 0 or 1, and it is the smallest unit of data. Eight bits form a byte, and kilobytes and megabytes are progressively larger multiples. Hence the bit is the smallest of the four.
ASCII, the American Standard Code for Information Interchange, uses seven bits and can therefore represent 128 characters. BCD and Gray code are binary coding schemes for digits, not general character sets. EBCDIC uses eight bits per character.
Multiply the fraction by two repeatedly and record the integer parts: 0.625 times 2 gives 1.25, then 0.25 times 2 gives 0.5, then 0.5 times 2 gives 1.0. Reading the integer parts gives 0.101. Checking: one half plus one eighth equals 0.625.
Primary memory such as RAM is connected directly to the processor and holds programs currently in use. Secondary memory such as disks and pen drives is reached through input and output operations and keeps data permanently. This distinction explains why both types are needed.
The leading bit is 1, so the number is negative. Invert the bits to get 00001001, add 1 to get 00001010, which is 10, so the original value is -10. The unsigned reading 246 exceeds the signed 8-bit range of -128 to 127.
A NAND gate is an AND gate whose result is inverted by a NOT stage. Since AND gives 1 for inputs 1,1, the inversion makes the NAND output 0. This is why NAND is called the universal gate, as other gates can be built from it.
Each unit is about 1024 times the one before it: a kilobyte is smaller than a megabyte, which is smaller than a gigabyte, which is smaller than a terabyte. The correct order therefore runs from KB up to TB. Any other arrangement contradicts this hierarchy.
An operating system is the system software that controls and coordinates hardware resources such as the CPU, memory and input/output devices, and it offers services on which application programs rely. A word processor is application software, a compiler is a language translator, and a device driver is a small program that controls one specific device.
Software is broadly divided into system software and application software. The operating system is system software because it manages hardware and provides a platform for other programs, whereas spreadsheets, photo editors and browsers are application software written to help the user perform a specific task.
A compiler translates the entire high-level source program into machine or object code in one go, and the resulting object program is then executed. An interpreter translates and executes statement by statement, an assembler translates assembly language, and a linker joins object modules into an executable.
File management is a core operating-system service: the OS organizes data into files and directories, tracks their locations on secondary storage and controls access to them. Web-page design, compilation and photo editing are tasks carried out by application software running on top of the operating system.
Multiprogramming allows several programs to reside in memory at once, and the operating system switches the CPU among them so that it is kept busy while one program waits for input or output. Spooling buffers output for a device, formatting prepares a disk, and defragmentation rearranges stored files.
A real-time operating system guarantees a bounded response time, so results are produced within a fixed deadline, which is essential for controlling machinery, vehicles and industrial processes. Batch systems group jobs for later processing, time-sharing systems divide CPU time among many interactive users, and distributed systems coordinate several networked computers.
The distinguishing feature of a command-line interface is that the user enters text commands, whereas a graphical user interface presents windows, icons, menus and a pointer so that actions can be chosen visually. Both interfaces let the user run programs and manage files; they differ in how instructions are given.
The operating system is the intermediary through which an application program requests memory, processor time and input/output services, and through which the user controls the machine. It does not change the physical clock speed of the processor, and documents are normally stored on secondary storage such as a hard disk rather than in ROM.
Linux is distributed with its source code available, so users may study, modify and redistribute it under the terms of its licence, which makes it open-source software. Windows, macOS and MS-DOS are proprietary products whose source code is not freely available to the public.
Open-source operating systems such as Linux are supplied together with their source code and a licence that permits modification and redistribution, so they meet both the cost and the source-code requirement. Proprietary systems withhold their source code, firmware is fixed low-level code, and a driver controls only one device.
Virtual memory management lets a program run even when it is larger than the available main memory by keeping only the needed portions in RAM and moving the rest to secondary storage. Job scheduling decides which job runs next, file allocation decides where file blocks are stored, and interrupt handling responds to signals from devices.
A file name usually has two parts, the name and the extension, separated by a dot. The extension is a convention that helps the operating system and the user identify the file type and therefore the application that should open it, but it does not hold the content, fix the size or provide encryption.
Virtual memory extends the apparent size of main memory by keeping inactive pages or segments on secondary storage and swapping them into RAM when needed. Caching keeps frequently used data in fast memory, spooling queues output for slow devices, and buffering holds data temporarily during transfer.
When a file is deleted, the operating system normally updates the directory and allocation information so that the blocks are marked as free, but the old data usually stays on the medium until new data overwrites it, which is why recovery tools can sometimes restore it. Deletion does not physically demagnetize the disk, move data to ROM or alter kernel code.
Round-robin scheduling assigns each ready process a fixed time slice, called a time quantum, and then moves it to the end of the queue, so every user is served in turn and the system appears interactive. Batch processing delays jobs, single-tasking operation runs one program only, and spooling concerns output devices rather than CPU sharing.
Utility programs are system-oriented tools that help maintain the computer, such as backup tools, disk cleaners, compression tools and antivirus scanners. They support the operating system rather than replace it, and they are distinct from application packages such as presentation software and from language translators such as compilers.
In batch processing, similar jobs are collected into a batch and processed one after another without user interaction, which suits repetitive bulk work such as monthly payroll. A real-time system is meant for strict deadlines, an interactive single-user system expects continuous user input, and a mobile operating system is designed for handheld devices.
A device driver is a program that contains the instructions needed to operate a particular hardware device, and the operating system loads the appropriate driver so that applications can use the device through standard services. Compilers and linkers are language-processing tools, and spreadsheets are application software.
An interpreter translates each statement and executes it immediately, which makes debugging convenient but generally slower at run time than a compiler, which translates the whole program once into object code that can then be executed repeatedly. The other statements misdescribe how interpreters and compilers work and what errors they detect.
The scheduler is the part of the operating system that selects a ready process from the queue and assigns it the processor according to the chosen scheduling policy. The file manager organizes stored data, the command interpreter reads and executes user commands, and device drivers control hardware.
Ctrl + S is the standard shortcut that saves the current document to its existing file name and location, overwriting the previous version. Other shortcuts control printing, creating a new document, and opening an existing file, so they do not perform a save.
Word wrap is the automatic movement of a word to the next line when there is not enough space at the right margin, so the user need not press Enter. It keeps the paragraph as a single unit that reflows when margins or fonts change.
The Centre alignment places each line at an equal distance from the left and right margins, which suits headings and titles. Align Left and Align Right push text to one margin, while Justify stretches all lines except the last to touch both margins.
A word processor saves ordinary text documents with the .docx extension in current versions, and older versions used .doc. The other extensions belong to spreadsheet, presentation and database programs respectively.
The insertion point is the blinking cursor marking the position where text will be inserted or deleted. It moves as the user types or clicks elsewhere in the document.
Pressing Enter inserts a paragraph mark and starts a new paragraph on the next line. Tab inserts a tab space, Shift modifies other keys, and Backspace deletes the character to the left of the cursor.