Q#1: Why the RAM needs continuous power supply in order to maintain the contents?
RAM is made up of integrated circuits so it needs continuous power supply. No mechanical process is involved in the working of RAM.
Q#2: Describe in detail the purpose and working of the main memory. Working of RAM:
When the processor or CPU gets the next instruction it is to perform, the instruction may contain the address of some memory or RAM location from which data is to be read (brought to the processor for further processing). This address is sent to the RAM controller. The RAM controller organizes the request and sends it down the appropriate address lines so that transistors along the lines open up the cells so that each capacitor value can be read. A capacitor with a charge over a certain voltage level represents the binary value of 1 and a capacitor with less than that charge represents a 0. For dynamic RAM, before a capacitor is read, it must be power-refreshed to ensure that the value read is valid. Depending on the type of RAM, the entire line of data may be read that the specific address happens to be located at or, in some RAM types, a unit of data called a page is read. The data that is read is transmitted along the data lines to the processor's nearby data buffer known as level-1 cache and another copy may be held in level-2 cache.
For video RAM, the process is similar to DRAM except that, in some forms of video RAM, while data is being written to video RAM by the processor, data can simultaneously be read from RAM by the video controller (for example, for refreshing the display image).
Purpose of RAM:
Random Access Memory (RAM) is simply called "Memory". It is directly readable by the Central Processing Unit (CPU) of a computer system. It's installed into the motherboard slots of a computer system. For a better performance and fast execution of programs a computer system should have large RAM. The RAM sizes of 256MB, 512 MB and 1GB are normal these days.
It's the only memory that is directly accessible by the Central Processing Unit (CPU) for reading/ writing. The CPU can't access the hard drives or CD drives attached with it. In case the CPU needs to access data that is residing in a hard disk or CD drive it's first transferred to RAM. If the RAM has got a small size then it'll store only a small amount of data and will load/re-load data continuously from the Data Source (hard disk or CD drive) to RAM. That's why a large sized RAM is desirable for the efficient performance and working of a computer system. If the RAM is small sized then applications and software that require a large memory area may work slowly. Multiple RAM's can be installed in a computer if the motherboard has multiple slots for RAM's
Q#3: Describe in detail the purpose and working of following Storage devices. Floppy disk
Hard disk Working of Floppy Disk:
Read Data From The Floppy Disk:
The steps followed by the floppy disk drive to read data from the floppy disk:
1. The user executes a command, or disk. The program requests information from the floppy disk. 2. The spindle motor in the floppy disk drive rotates the floppy disk.
3. The stepper motor moves the read write head over the required track and the read write head reads the data from the floppy disk.
4. The floppy disk drive sends the data to the microprocessor for processing. 5. The spindle motor stops rotating the floppy disk in the floppy disk drive. Write data on the floppy disk:
The steps followed by the floppy disk drive to write data on the floppy disk:
1. The user executes a command, or the program sends data to be written on the floppy disk. 2. The spindle motor in the floppy disk drive rotates the floppy disk.
3. The stepper motor moves the read write head over the required track for the read write head to read the track address from the floppy disk for storing the data.
4. The erase coils located on the read write head erases the data from the track. 5. The write head is wound up.
6. The write head converts the binary data into electromagnetic impulses and writes the data on the floppy disk. 7. The spindle motor stops rotating the floppy disk in the floppy disk drive.
Working of Hard Disk:
A hard disk uses rigid rotating platters. Each platter has a planar magnetic surface on which digital data may be stored. Information is written to the disk by transmitting an electromagnetic flux through an read-write head that is very close to a magnetic material, which in turn changes its polarization due to the flux. A typical hard disk drive design consists of a central axis or spindle upon which the platters spin at a constant rotational velocity. The associated electronics control the movement of the read-write armature and the rotation of the disk, and perform reads and writes on demand from the disk controller. The sealed enclosure protects the drive internals from dust, condensation, and other sources of contamination. Contrary to popular belief, a hard disk drive does not contain a vacuum. Instead, the system relies on air pressure inside the drive to support the heads at their proper flying height while the disk is in motion.
Q#4: Define data rate and seek time.
Data rate is also known as data transfer rate or throughput. It refers to the speed with which the data can be transmitted from one device to another. Data rates are commonly measured in megabytes (MB) per second. The data rates for a typically hard disk ranges between 5 to 40 megabytes per second.
Seek time refers to the total span of time between a file request by the CPU to the point when the first byte of the file is sent to the CPU. This is one of the several delays associated with reading or writing data on a computer's disk drive. In order to read or write data in a particular place on the disk, the read/write head needs to manoeuvre to the precise location of the disk platter. This process is known as "seeking", and the time it takes for the head to move to the right place is referred to the "seek time". A typical seek time for a hard disk is about 9 to 15.
Majority of all hard disk today support a technology known as S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) which helps to predict imminent disk failures so that users can be alerted to take preventive actions before the disk fails completely.
Q#5: Describe in detail the purpose and working of the following backing storage devices. Compact disk
Magnetic disk Working of Compact Disk:
The laser beam reads coded information from the compact disc. The reading is kept accurate by the servo processor. The data from the reading is sent to the decoder, where it is converted to regular digital information. A digital filter then removes noise. The DAC, the most important part of the CD player, converts the digital data to an analogue audio wave. After an analogue filter removes noise, this wave is sent to the loudspeakers for reproduction as sound. The
microprocessor controls features, such as volume, balance, tone, etc.
A CD player has a very precise tracking mechanism which keeps the laser and lens focused on the very narrow track. This tracking mechanism moves the laser assembly linearly, but data is stored in one long spiral that starts at the center of the compact disc and moves out. As the CD player reads the data, the drive motor must precisely vary the rotation speed of the CD so the data can be read at a constant rate.
Working of Magnetic Disk:
A magnetic disk is a metal or plastic disk coated with magnetic material. Data is recorded into the magnetic material in machine code. Disks have become popular due to their random access. These disk spin in the disk drives Read/Write heads moving on the disk along its radius can read data at any location under the heads.
Reading data from the disk means converting the magnetized data to electrical impulses that can be sent to the processor. Writing data to disk is the opposite: sending electrical impulses from the processor to be converted to magnetized spots on the disk. The surface of each disk has concentric tracks on it. The number of tracks per surface varies with the particular type of disk.
Q#6: Explain using a labeled diagram, the concept of track and sector when describing magnetic disk storage. Data is stored on the surface of a platter in sectors and tracks.
Tracks are concentric circles, and sectors are pie-shaped wedges on a track, like in figure given below:
A typical track is shown in yellow; a typical sector is shown in blue. A sector contains a fixed number of bytes, for example, 256 or 512. Either at the drive or the operating system level, sectors are often grouped together into clusters.
Q#7: Explain the purpose of the following and draw a diagram showing their relationship. Cache memory
Hard disk Magnetic tape Cache Memory Purpose:
The main function of cache memory is to speed up the working mechanism of computer and it is placed between the main memory and CPU.
Purpose of Hard Disk:
The Hard drive is commonly known as the Hard Disk Drive. It is one of the most essential features of a computer. It is a storage device that can preserve the information that has been stored into, even when this device is not powered. In other words we can say that a hard disk is a non-volatile storage device.
The basic purpose of the magnetic tape is to store large amount of data. It is mostly used for backing up of large data in data centers or in corporate companies.
Q#8: Explain why secondary storage is needed in computer system?
Unlike primary storage; secondary storage is not directly accessed by the CPU. Examples of secondary storage are hard drives, CD drives, flash, etc. Anything that can store data without losing it upon power down (non-volatile storage) is considered secondary storage.
It is a necessary component of a personal computer. Without it we would have no place to store our data. Q#9: explain the purpose of the following
High Level Formatting Low Level Formatting
High Level Formatting: In the high level format the data is just deleted from the hard disk drive.
The high level formatting of the storage media is easy and quickly performed. The high level format in case of the Disk Operating System or popularly called as the DOS is done by the command that is known as the „format‟.
The difference between the low level formatting and the high level formatting is that the low level formatting of the disk behaves as if the data is erased and again overwritten with some other data.
Suppose is the data is just deleted then also resides in the disk. The only thing is that it is not visible. The data is
permanently deleted only when some other data is overwritten to the location of the data that was deleted. Hence the data in case of the low level formatting acts as if it is overwritten. This is the main difference between the low level formatting and the high level formatting.
Low Level Formatting: In low level formatting the data is not overwritten; it just appears that it is overwritten. In other words the data is completely or permanently deleted from the storage media over which the low level formatting is done. Q#10: What RAM is random access?
Why Random Access:
RAM is called "random access" because any storage location can be accessed directly.
On magnetic tape an item of data could only be accessed by starting from the beginning of the tape and finding an address sequentially.
RAM is organized and controlled in a way that enables data to be stored and retrieved directly to specific locations. Note that other forms of storage such as the hard disk and CD-ROM are also accessed directly (or "randomly") but the term random access is not applied to these forms of storage.
Q#11: A nine class student has a home computer. What storage device he will use in his system? Why it is needed? He will use hard disk to store data due to following reasons.
Hard disk store massive amount of data Hard disk is permanent storage device Hard disk is less expensive
MCQ’s: Chapter No.04
1. Computers need to have some kind of --- devices to store large programs and data (a).storage (b).output (c).scanning (d).input
2. In digital computers program first needs to be executed is loaded in --- and then instructions are executed (a).CPU (b).memory (c).HDD (d).USB
3. ---memory is very fast but limited in capacity (a).primary (b).secondary (c).USB (d).Hard Disk
4. Main memory consists of millions of cells each cell can store a --- (a).byte (b).bit (c).kilobyte (d).megabyte
5. Memory cells are logically organized into group of 8-bits called --- (a).byte (b).bit (c).kilobyte (d).megabyte
6. Each --- of memory has a unique number assigned to it (a).byte (b).bit (c).kilobyte (d).megabyte
7. The number assigned to memory location is called --- of that byte (a).location (b).space (c).address (d).all of these
8. Main memory is --- access storage device
(a).Sequential (b).direct (c).indirect (d).all of these 9. Computers have two kind of main memory --- and ---
(a).RAM, ROM (b).RAM, Floppy (c).RAM, CDROM (d).all of these 10. Memory locations of main memory can be accessed in --- time
(a).different (b).same (c).two times (d).unequal time
11. CPU can perform two type of operations on RAM --- and --- (a).read, write (b).read, execute (c).write, execute (d).write, burn
12. During --- operation the contents of the main memory are copied to the CPU register (a).read (b).write (c).execute (d).add
13. During --- operation the content of the CPU register are copied to memory location (a).read (b).write (c).execute (d).add
14. RAM is usually built using two different technologies--- and ---
(a).ROM,RAM (b). DRAM, SRAM (c).EEPROM,RAM (d).RAM, EPROM 15. Data stored in a --- needs to be refreshed periodically
(a). DRAM (b).SRAM (c).RAM (d).ROM
16. SRAM is faster than --- but it is more expensive
(a). DRAM (b).SRAM (c).RAM (d).ROM
17. Content of the --- need not to be refreshed periodically
(a). DRAM (b).SRAM (c).RAM (d).ROM
18. Cache memory is built using the --- technology
(a). DRAM (b).SRAM (c).RAM (d).ROM
19. The very fast memory inside the CPU chip is called as --- (a). DRAM (b).cache (c).RAM (d).ROM 20. Contents of the memory are lost so RAM is a ---
(a).erasable (b).Volatile (c).read-only (d).Write-only 21. ROM is the abbreviation of ---
(a).Read Only Memory (b).Random only Memory (c).Read only Mass (d).Random only Mass
22. --- is used to save frequently used instruction and data (a).RAM (b).ROM (c).EPROM (d).Hard Disk 23. EEPROM stands for---
(a).Electron Erase ROM (b). Electronically programmable ROM (c). electronically erasable programmable ROM (d).Electronic EROM
24. ROM is --- as the content of the memory are not lost upon switch off the circuit (a).erasable (b).Volatile (c).read-only (d).Nonvolatile
(a).System Bus (b).Address Bus (c).Control bus (d).data bus
26. Data bus, address bus and control bus are collectively called as --- bus (a).System Bus (b).Address Bus (c).Control bus (d).Data bus
27. When CPU want to read some data from memory it places the read request on the --- bus (a).System Bus (b).Address Bus (c).Control bus (d).Data bus
28. Address of the byte or word needed is placed on --- bus (a).System Bus (b).Address Bus (c).Control bus (d).Data bus
29. Memory unit read the address required to the CPU and places the required data on --- bus (a).System Bus (b).Address Bus (c).Control bus (d).Data bus
30. Main memory consists of --- circuits
(a). electronic (b).analogue (c).manual (d).mechanical 31. Main memory is accessible without using any --- components (a). electronic (b).analogue (c).manual (d).mechanical 32. 1 nibble is equal to ---
(a).2 bits (b).4 bits (c).8 bits (d).1 byte 33. 1byte is equal to ---
(a).2 bits (b).4 bits (c).8 bits (d).1 byte 34. 1 terabyte is equal to --- bytes
(a).1000 bytes (b).2^40 bytes (c). 2^30 bytes (d). 2^20 bytes 35. 1GB is equal to --- bytes
(a).1000 bytes (b).2^40 bytes (c). 2^30 bytes (d). 2^20 bytes 36. 1MB is equal to --- bytes
(a).1000 bytes (b).2^40 bytes (c). 2^30 bytes (d). 2^20 bytes 37. 1KB is equal to --- bytes
(a).1000 bytes (b).2^10 bytes (c). 2^30 bytes (d). 2^20 bytes 38. The bit at the left end is often called the high order bit or ---
(a).MSB (b).LSB (c).DSB (d).All of these
39. The bit at the right end is often called the low order bit or --- (a).MSB (b).LSB (c).DSB (d).All of these
40. FDD stands for ---
(a).First Disk Drive (b). Floppy Disk Drive (c). Fragile Disk Drive (d).All of these Answer Key MCQs:
1.a 2.b 3.a 4.b 5.a 6.a 7.c 8.b
9.a 10.b 11.a 12.a 13.b 14.b 15.a 16.a 17.b 18.b 19.b 20.b 21.a 22.b 23.c 24.d 25.a 26.a 27.c 28.b 29.d 30.a 31.d 32.b 33.c 34.b 35.c 36.d 37.b 38.a 39.b 40.b
CHAPTER NO- 4 FILL IN THE BLANKS 1. Computer storage is divided into two main classes____________. 2. The capacity of a storage device is expressed as number of_____. 3. 1 nibble=___________________bits.
4. 1 byte-____________________bits. 5. 1 kilobytes=_________________bytes. 6. 1 megabytes =______________kilobytes. 7. 1 gigabytes =_______________megabytes. 8. 1 terabytes =______________ gigabytes.
9. __________ is an extension of the central processing unit (CPU) and is directly accessible to it.
10. The______of a storage device is expressed as number of bytes, characters or bits.
11. ________is a memory in which each element of information has its own address and from which that element can be retrieved easily and quickly by using that address.
12. CMOS stands for__________________________________. 13. SIMMs stands for__________________________________.
14. A________________memory chip less than one-fourth the size of a postage stamp can store more than 4,000,000 bits, or more than 400,000 characters of data.
15. Data can be accessed from ___________without any mechanical movement at electronic speed, close to the speed of light.
16. SRAM stands for_______________________________ . 17. DRAM stands for________;_____________________________. 18. DIP stands for_______________________________________. 19. DIMMs stand for_____________________________________. 20. ROM stands for_____________________________________.. ANSWERS
1. i) Main storage or primary memory ii) Secondary storage or secondary memory. 2. Bytes, characters or bits 3.(4) 4. 5. 1024 6. 1024 7. 1024 8. 1024 9. Main memory 10. Capacity 11. RAM 12. Complementary Metal Oxide Semiconductor 13. Single in-line memory modules 14. CMOS 15. RAM 16. Static random access memory 17. Dynamic random access memory 18. Dual in line pin 19. Dual in-line memory modules 20. Read only memory