Topic 2 (hardware)

Topic 2 (hardware)

1. CPU

   • ALU
     • An arithmetic logic unit (ALU) is a digital electronic circuit that performs arithmetic and bitwise logical operations on integer binary numbers. It is a fundamental building block of the central processing unit (CPU) found in many computers. This is in contrast to a floating-point unit (FPU), which is a digital circuit that operates on floating point numbers with the aid of one or more internal ALUs. Powerful and complex ALUs are often used in modern, high performance CPUs, FPUs and graphics processing units (GPUs). A single CPU, FPU or GPU may contain multiple ALUs.
   • cycle
     • fetch
     • decode
     • execute

2. primary storage

   • RAM
     • Random-access memory (RAM /ræm/) is a form of computer data storage. A random-access memory device allows data items to be read and written in approximately the same amount of time, regardless of the order in which data items are accessed. In contrast, with other direct-access data storage media such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement delays.

3. secondary storage

   • HDD
     • The use of magnetic media to store data goes back to 1898 when audio was stored on a magnetised wire wrapped around a drum, but it is still the most widely used secondary storage device used on modern computers. The magnetic hard disk is a magnetised rigid plate or stack of plates with heads to read the data as the platters spin around. They spin at around 7200 RPM. The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation. The data is read by detecting the changes in direction.
   • SSD
     • A solid-state drive (SSD) (also known as a solid-state disk though it contains no actual disk, nor a drive motor to spin a disk) is a data storage device that uses integrated circuit assemblies as memory to store data persistently. SSD technology uses electronic interfaces compatible with traditional block input/output (I/O) hard disk drives, thus permitting simple replacement in common applications. Additionally, new I/O interfaces, like SATA Express, have been designed to address specific requirements of the SSD technology.