what is execution cycle of CPU?difference between RAM and ROM.explain by the primary memory and secondary memory?

what is execution cycle of CPU?difference between RAM and ROM.explain by the primary memory and secondary memory?

EXECUTION CYCLE OF CPU:                                                       to further understand the concept  of execution cycle, conside... 23:40

EXECUTION CYCLE OF CPU:
                                                      to further understand the concept  of execution cycle, consider the following example:
                                          when a student enters a math problem into the calculator of a computer, it goes to the memory of a computer. CPU solves it in a cycle of 4 steps.
step 1.      the control unit (CU) fetches the instructions for math's problem and data from the memory of a computer.
step 2.       the control unit decodes the instructions for math's problem and data then send to ALU.
step 3.        ALU performs calculations on the data.
step 4.         the results of math's problem are stored in memory.
the result in the memory operators on the calculator screen.
MEMORY IN A COMPUTER SYSTEM:
                                                                  memory consists of the devices that store instructions and the data needed by th

e CPU for calculations. after calculations, it is again stored in the memory for future use'
memory in a computer system in divided into two categories:
. primary memory (short term)                                        .  secondary memory ( long term)
let's try understand the difference between primary memory and secondary memory.
Primary Memory:
                                  primary memory is also known as the main memory of the computer. the data stored in it is quickly accessed by the CPU as it is directly linked to it. it is used for temporary storage of data, see fig:8. primary memory is further divided into two types:
1.        random access memory (RAM)
2.        read only memory (ROM)
let's further differentiate RAM and ROM
                    RAM                                                                                           ROM
.   it is link with CPU.                                                              . it is built within the CPU.
.  it allows read and write functions.                                     .  it is read only.
.   the data stored in it is not permanent.                             .  it is permanent in nature,
it get lost when computer is switched off.                              data does not get lost when
.   it is less expensive.                                                         computer is switched off.
.  SRAM, OR and DRAM are the example of RAM.                  .  it is more expensive.
                                                                                                    .  BloS is the example of
                                                                                                          ROM.
but over all primary memory is expensive and has limited storage capacity. a cheaper storage medium of permanent nature and large storage capacity is needed to be used in the computer to store large amounts of data. that is why, to increase the storage capacity of permanent nature, secondary memory is used.
SECONDARY MEMORY:
                                        secondary memory is also known as permanent memory or long term memory. it is different from primary in a sense that it is the place where data or information is stored permanently and transferred to the CPU for processing when needed. as primary memory is the only memory that is directly linked to the CPU' so data or information is transferred to the primary memory first and then control unit of CPU transfers it to the ALU for processing.