What Every Programmer Should Know About Memory

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What Every Programmer Should Know About Memory

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Re: What Every Programmer Should Know About Memory

Unread postby zainab khalid » Fri Mar 27, 2015 5:40 pm

Computer memory is a permanently or temporary storage area. It contains the data or information that CPU needs.
Memory is typically of the same kind of switches which is known as transistors. Switches are present in two states, on or off. In which on state represents "1" and off state represents "0".So the one of transistor can represent one of two digits.
Our computer memory is divided into several different types of memory, but the most important are known as "RAM AND ROM". but in which we discus about the RAM....

RAM is known as Random access memory. In which we can access any memory cell directly if we know about the row and column.
RAM is used for reading or writing to file storage. Solid-state disks, in our android devices, people use as a hard drives in their computers are faster than normal computer hard drives, But using to cache the data we need a lot slower that using dedicated, solid-state RAM.
RAM is so much cheap.
RAM is volatile, that is instructions and data holds in memory are lost once the computer is powered down.

Their are two types of RAM, Static RAM and Dynamic RAM.
Comparison of static RAM and dynamic RAM:-
1- dynamic RAM needs to be refreshed thousands of times per second but static RAM does not need to be refreshed.
2- DRAM supports access times 60 nanoseconds and Static RAM supports access times 10 nanoseconds.
3- Static RAM is faster, but its not as commonly used as DRAM because its so much more expensive.
4- Static RAM and DRAM are both volatile, but they lost their contents when the power is turned off.

Android is not doing a good job managing memory on higher RAM devices.
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Re: What Every Programmer Should Know About Memory

Unread postby Mehran khan » Sun Mar 29, 2015 5:52 pm

memory refers to the devices used to store information for use in a computer.The computer memory is a temporary storage area. It holds the data and instructions that the Central Processing Unit (CPU) needs. Before a program can be run, the program is loaded from some storage medium into the memory. This allows the CPU direct access to the program.

Two types of Memory

RAM:-RAM stand for random access memory.RAM is volatile memory because it needs a constant power supply to hold data.RAM holds data for a short time.When the power loss.a RAM will ALSO lose the information stored on it.

ROM:-RAM stand for Random only memory permanently stores its data, even when the computer is shut off. ROM is called non-volatile memory because it never loses its contents. ROM holds instructions that the computer needs to operate. Whenever the computer's power is turned on, it checks ROM for directions that help it start up, and for information about its hardware devices.
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Re: What Every Programmer Should Know About Memory

Unread postby M.HAMZA(13963) » Fri Apr 10, 2015 8:42 pm

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What every programmer should know about memory
Computer memory is a permanent storage and temporary storage area.it contains that information or data where the computer is needed.
Memory is typically some kind of switches which is called as transistors. Switches shows 2 states on and off, in which on states shows “1” and off states shows “0”. So one transistor is shows 2 digits.
Computer memory is divided into different types, but most important is RAM and ROM.
ROM is known as read only memory. In this memory, data can be written on rom chip and can’t be removed and can only to read.
ROM is non-volatile memory.
ROM retains its contents even when computer is turned off.
Some personals computers contain a small amount of ROM which stores critical programs.
RAM is known as random access memory. In this memory, data can be written on ram chip and can be removed and can read and write.
Ram is volatile memory.
RAM cannot retain its contents when computer is turned off.
RAM is much cheaper.
In our android devices, peoples use a hard drives in their computers are faster than normal computer hard drives, but using to cache the data we need a lot of slower that using dedicated solid-state RAM
Android is not good for high RAM devices .
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Re: What Every Programmer Should Know About Memory

Unread postby sufyan9458 » Tue Apr 21, 2015 8:00 am

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Computer memory
The computer memory is a temporary storage area. It holds the data and instructions that the Central Processing Unit (CPU) needs. Before a program can be run, the program is loaded from some storage medium into the memory .It is device that is used to store data or programs on a temporary or permanent basis for use in an electronic digital computer.Computers represent information in binary code 0
It is an essential element of a computer. Without its memory, a computer is of hardly any use. Memory plays an important role in saving and retrieving data. The performance of the computer system depends upon the size of the memory. Memory is of following types:

1. Primary Memory / Volatile Memory: Primary Memory is internal memory of the computer. RAM AND ROM both form part of primary memory. The primary memory provides main working space to the computer .The following terms comes under primary memory of a computer are discussed below:

Random Access Memory (RAM): The primary storage is referred to as random access memory (RAM) because it is possible to randomly select and use any location of the memory directly store and retrieve data. It takes same time to any address of the memory as the first address. It is also called read/write memory. The storage of data and instructions inside the primary storage is temporary. It disappears from RAM as soon as the power to the computer is switched off. The memories, which lose their content on failure of power supply, are known as volatile memories .So now we can say that RAM is volatile memory.

Read Only Memory (ROM): There is another memory in computer, which is called Read Only Memory (ROM). Again it is the ICs inside the PC that form the ROM. The storage of program and data in the ROM is permanent.The ROM can only be read by the CPU but it cannot be changed. The basic input/output program is stored in the ROM that examines and initializes various equipment attached to the PC when the power switch is ON. The memories, which do not lose their content on failure of power supply, are known as non-volatile memories. ROM is non-volatile memory.

PROM: There is another type of primary memory in computer, which is called Programmable Read Only Memory (PROM). You know that it is not possible to modify or erase programs stored in ROM, but it is possible for you to store your program in PROM chip. Once the programmers’ are written it cannot be changed and remain even if power is switched off. Therefore programs or instructions written in PROM or ROM cannot be erased or changed.

EPROM: This stands for Erasable Programmable Read Only Memory, which overcome the problem of PROM & ROM. EPROM chip can be programmed time and again by erasing the information stored earlier in it. When the EPROM is in use information can only be read.

Cache Memory: The speed of CPU is extremely high compared to the access time of main memory. Therefore the performance of CPU decreases due to the slow speed of main memory. To decrease the mismatch in operating speed, a small memory chip is attached between CPU and Main memory whose access time is very close to the processing speed of CPU. It is called CACHE memory. CACHE memories are accessed much faster than conventional RAM. It is used to store programs or data currently being executed or temporary data frequently used by the CPU. So each memory makes main memory to be faster and larger than it really is. It is also very expensive to have bigger size of cache memory and its size is normally kept small.

Registers: The CPU processes data and instructions with high speed; there is also movement of data between various units of computer. It is necessary to transfer the processed data with high speed. So the computer uses a number of special memory units called registers. They are not part of the main memory but they store data or information temporarily and pass it on as directed by the control unit.

2. Secondary Memory / Non-Volatile Memory:  Secondary memory is external and permanent in nature. The secondary memory is concerned with magnetic memory. Secondary memory can be stored on storage media like floppy disks, magnetic disks, magnetic tapes, This memory can also be stored optically on Optical disks - CD-ROM. The following terms comes under secondary memory of a computer are discussed below:

Magnetic Tape: Magnetic tapes are used for large computers like mainframe computers where large volume of data is stored for a longer time. The cost of storing data in tapes is inexpensive. Tapes consist of magnetic materials that store data permanently. It can be 12.5 mm to 25 mm wide plastic film-type and 500 meter to 1200 meter long which is coated with magnetic material. The deck is connected to the central processor and information is fed into or read from the tape through the processor. It’s similar to cassette tape recorder.

Magnetic Disk Magnetic disks used in computer are made on the same principle. It rotates with very high speed inside the computer drive. Data is stored on both the surface of the disk. Magnetic disks are most popular for direct access storage device. Each disk consists of a number of invisible concentric circles called tracks. Information is recorded on tracks of a disk surface in the form of tiny magnetic spots. The presence of a magnetic spot represents one bit and its absence represents zero bit. The information stored in a disk can be read many times without affecting the stored data. So the reading operation is non-destructive. But if you want to write a new data, then the existing data is erased from the disk and new data is recorded.  For Example-Floppy Disk.

Optical Disk: With every new application and software there is greater demand for memory capacity. It is the necessity to store large volume of data that has led to the development of optical disk storage medium.
Introduction to Computer Memory
Since computers represent everything as numbers, computer memory only has to be able to store numbers.The computer memory are two types primary computer memory; secondary
Primary memory is considered as a main memory that is accessed directly by the computer, so as to store and retrieve information. Secondary memory is considered as an external or additional memory, this memory is not directly accessed by the CPU because, the secondary memory is an external storage device, It can be used as a permanent memory, because even the computer is turned off we can retrieve the information
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