Lecture Notes

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• CPU
• Hertz (Hz), KHz, MHz, GHz
• Bus
• Input
• Output

• Primary memory
• Secondary memory
• Volatile/non-volatile
• Binary Digit
• Bit

• What is a computer / basic diagrams as discussion catalyst.
• Computers do two functions:
• Accepting input
• Yielding an output

• Internal components of a computer:
• CPU – "Central Processing Unit" the brains of the computer
• Calculations are carried out by the cpu
• Performance is based on two characteristics:
• Speed: gauged in Hz (hertz): fastest machines now at 2.2 GHz.
• Number of bits processed per cpu cycle. (32-64 bits for standard PC’s).
• RAM – "Random access memory" : also referred to as Primary Memory.
• Semi-conductor, therefore volatile. Volatile refers to the loss of stored data when power is lost from memory.
• DDR RAM –duel data rate RAM
• Very fast…also very expensive.
• ROM – "Read only memory"
• Silicon based memory
• Set of instructions which aid in system start up contained on this memory.
• Because of this function, this type of memory can’t be changed.
• Hard Disk: now referred to as secondary memory.
• Magnetic media, therefore this is non-volatile memory.
• Slow read / write process as compared to RAM
• Very economical data storage.
• Bus: a device which conceptually "connects" the components listed above: allows transfer of data between them.
• A clock controls bus operations.
• Once again it is important to note that the number of bits which can be transferred by bus per cycle is very important concerning the speed at which the bus can function.
• Bits:
• Logic derived from strategies of representation, because all information is communicated with two symbols: 1’s and 0’s
• 1’s are communicated by the presence of an electrical impulse, 0’s by the lack of electrical impulse.
• 1’s and 0’s can represent real numbers, whole numbers, characters, or states of true and false.

• So, one can now think of either a single 1 or a single 0 as being called a bit.