Grade 11 Text Book LU 3

Question 1

What is the start-up and boot sequence of a computer?

Answer 1

When a computer is switched on, and before the operating system is loaded, the hardware devices that will be used by the computer need to be checked. Once they are deemed to be correct, the operating system which resides on the main hard drive of the computer will be loaded in RAM together with the drivers for the hardware devices. A boot sequence is this initial set of operations that the computer performs when it is switched on.

Question 2

What is a boot loader?

Answer 2

The program that performs the boot sequence which ends with the entire operating system being loaded is known as the boot loader (or bootstrap loader).

Question 3

What is BIOS?

Answer 3

BIOS is short for Basic Input-Output System. It is low-level software that resides in a non-volatile ROM chip on a computer’s motherboard.

Question 4

What is firmware?

Answer 4

Software that permanently resides on ROM is known as firmware.

Question 5

What is BIOS responsible for?

Answer 5

The BIOS is responsible for the POST, or Power-On Self-Test and loading the operating system. When the computer turns on the following process is followed:
* The BIOS begins the Power-On Self-Test to check the hardware.
* An inventory of the hardware connected to the computer is obtained from the CMOS (Complementary Metal-Oxide-Semiconductor).
* The hardware is tested to determine if it is functioning correctly.
* The BIOS locates the Master Boot Record (MBR), a section of code usually stored on the hard disk drive. The MBR is responsible for loading and executing the operating system kernel, which continues with the start-up procedure.

Question 6

What is a Kernel?

Answer 6

The kernel is the core of a computer’s operating system that remains in RAM. It is responsible for input/output requests from software, translating them into instructions for the CPU. It handles memory and peripherals like keyboards, monitors, printers, and speakers.

Question 7

What is CMOS?

Answer 7

CMOS is a battery-backed, volatile memory that stores:
* hardware settings - the types of hardware installed on your computer such as the disk drive.
* user settings - the current date and time.

Question 8

What is CMOS responsible for in the boot up process?

Answer 8

To obtain data about the system.

Question 9

What is UEFI?

Answer 9

Unified Extended Firmware Interface (UEFI). Not all hardware supports UEFI but UEFI can emulate BIOS so it can boot old Operating Systems. Backwards compatible

Question 10

Advantages of UEFI over BIOS

Answer 10

• The UEFI firmware can boot from drives of 2.2 TB or larger.
• UEFI can run in 32-bit or 64-bit mode which has more address space than BIOS; this means that the boot process is faster.
• UEFI setup screens can be more user-friendly than BIOS settings screens, including graphics and mouse cursor support. BIOS doesn’t have the capability of using mouse and graphics drivers.

Question 11

UEFI features that BIOS doesn’t have?

Answer 11

• It supports Secure Boot, which means the operating system can be checked for validity to ensure no malware has tampered with the boot process.
• It can support networking features right in the UEFI firmware itself, which can aid in remote troubleshooting and configuration, which is not possible with a traditional BIOS.
• It’s not just a BIOS replacement either - UEFI is essentially a tiny operating system that runs on top of a computer’s firmware, and it can do a lot more than a BIOS.
• It may be stored in flash memory on the motherboard or it may be loaded from a hard drive or network share at boot.

Question 12

What is a interrupt?

Answer 12

An interrupt is a signal sent to the CPU from hardware or software indicating the need for the CPU’s attention. Can be generated by software or hardware.

Question 13

What is an example of a software interrupt

Answer 13

Dividing by zero, square rooting a negative number or when an Input / Output (I/O) is required. It can also occur when the timer indicates that a process has had its allocated amount of CPU cycles.

Question 14

What is an example of a hardware interrupt

Answer 14

An example of a hardware interrupt is when a signal is sent from a device, such as the keyboard indicating that a key has been pressed, or a printer indicating that it has run out of paper.

Question 15

What will a device do if there are multiple interrupt requests?

Answer 15

When the device has multiple interrupt outputs to handle, it will handle them in the order of their relative priority.

Question 16

What is a IRQ?

Answer 16

Every device has a unique Interrupt Request Number (IRQ) which the CPU uses to identify which device is interrupting it. For example, the Keyboard has IRQ 1

Question 17

What is a IO Range?

Answer 17

An IO Range is a buffer, a temporary storage area in RAM, used to speed up a slow input/output device.

Question 18

What is an example of an IO Range?

Answer 18

Reading a file in programming: when you read from a text file, instead of reading line by line, will take many CPU cycles just for one line. It is much more efficient to load the entire file into a buffer in memory so as not to violate the very important rule that the CPU is never idle. When you write to a file, instead of writing line by line, the entire file is written to a buffer, and when the close file command is called, the file is saved to secondary storage and the buffer is flushed (cleared) for the next similar processing request.

Question 19

What is processing techniques?

Answer 19

Processing techniques, used by software and hardware, are designed to optimise the efficiency of a computer system.

Question 20

What is Multitasking?

Answer 20

With multitasking, there are several programs stored in the computer’s RAM and the CPU switches very short bursts of processing time between all the running programs so that the user seems to be running several programs simultaneously. Multiple tasks on a single processor.

Question 21

What is process scheduling?

Answer 21

Involves giving each running process its fair share of the CPU’s time without letting any process remain suspended for too long.

Question 22

How does a computer allow multitasking to work?

Answer 22

• A process occupies a certain amount of RAM. It also makes use of registers within the CPU and operating-system memory space.
• When two processes are multi-tasking, the operating system allots a certain number of CPU execution cycles to one program.
• After that number of cycles, the operating system makes copies of all the registers used by the processes and notes the point at which the process paused in its execution.
• It then loads all the registers used by the second process and allows it a certain number of CPU cycles.
• When those are complete, it makes copies of all the registers used by the second program and loads the first program.

Question 23

What is multithreading?

Answer 23

One program can have several different threads (parts of a program that run independently) running at the same time. This is called multithreading.

Question 24

What is Virtual Memory?

Answer 24

When RAM is full the operating system can use a section of the hard disk as an extension of RAM.
This virtual memory extends the number of addresses that RAM has and requires pages to be swapped between RAM and the hard disk. This is the opposite of caching.

Question 25

What are translators?

Answer 25

Translators are software programming tools that convert code into another type of code; they translate source code into code that the CPU can understand. A translator, in software programming terms, is a generic term that could refer to a compiler, assembler, or interpreter.

Question 26

What is High-Level languages?

Answer 26

High-level languages contain a high level of abstraction where the underlying workings of the computer are hidden from the programmer and are closer to human languages. High-level languages deal with variables, arrays, objects, complex arithmetic or Boolean expressions, methods and loops.

Question 27

What is Low-Level Languages

Answer 27

Low-level languages are closer to the machine language and generally refer to machine language (machine code) or assembly language. Machine language is at the lowest level, because it is the actual binary code of 1s and 0s that the computer understands. Assembly languages are low-level languages which are translated into machine code by an assembler. Each assembly language instruction corresponds to one machine language instruction, but assembly.

Question 28

What are interpreters?

Answer 28

Interpreted languages are read and then executed directly, with no compilation stage. A program called an interpreter reads each program line, converts it to machine code, and executes it; the machine code is then discarded, to be interpreted anew if the line is executed again. Examples of interpreted languages are Python and JavaScript.

Question 29

Advantage + Disadvantage of interpreted languages

Answer 29

The advantage of an interpreted language is that if the code has any syntax errors, it will still run up till the line of code with the error. The disadvantage is that each time you need to run the program it must be re-interpreted line by line and then executed slowing down the process.

Question 30

What is machine code generation?

Answer 30

Some compilers compile source code directly into machine code by creating a new file called the object code. The object code is machine-dependent meaning that the compiled program can only be executed on a machine for which it has been compiled. For example, Delphi is compiled into an .exe file which can only be run on Windows based operating systems.

Question 31

What is intermediate representations?

Answer 31

This process occurs in two steps: the language is first compiled to an intermediate representation called a bytecode and then secondly the representation can be executed without the need to re-read the source file. The bytecode must then be interpreted or further compiled to execute it. For example, Java source code is compiled into a byte code file with the extension .class. This file is then interpreted using the Java Virtual Machine.

Question 32

What is Machine Cycle?

Answer 32

Most programmers develop code using high-level languages like Java, C++, Ruby, BASIC or Python. High-level languages need to be translated using a compiler or interpreter into a binary code before the CPU can execute them.

Question 33

4 stages of processing

Answer 33

• FETCH a program instruction from memory (RAM or cache)
• DECODE (understand) the instruction (using the CPU’s instruction set)
• EXECUTE the instruction, using data, if necessary
• STORE the result obtained back in the main memory or send to an output device.