Page 22 - Computer Science V2.0 Class 11

Give a one-word answer for the following:
1. The high-speed temporary storage in the CPU.
2. The type of operations in ALU that return True or False.
3. An eight-bit sequence.
4. A non-volatile memory that stores instructions for booting.
5. A type of memory that stores frequently used instructions.

C. Secondary Memory
In contrast to RAM, the secondary memory stores data and instructions in the computer system permanently. Even
though ROM also stores data permanently, it is very expensive and does not allow data modification. The secondary
memory is used to store data and instructions for the long term as it is non-volatile. Further, the secondary memory has
a much larger storage capacity than the primary memory. It is slower but cheaper than primary memory. However, the
CPU cannot access secondary memory directly. The contents stored on secondary memory must first be loaded into
the main memory for processing by the CPU. Secondary memory includes hard disks, compact discs (CDs), memory
cards, pen drives, and solid-state drives (SSDs). Further, apart from the aforementioned secondary storage media that
is owned by a computer service centre or a user of a computer system, nowadays, data is also stored in a virtual space
or cloud, which is managed by service providers like Google, Microsoft, and Amazon. Google Drive is an example of
virtual storage.

1.4.3 Data Transfer Between Memory and CPU

Data is transferred between different components of a computer system (CPU to primary memory and vice versa or
primary memory to secondary memory, or cache memory to CPU and vice versa) using physical connections called
buses. There are three types of buses:

Data Bus: It is used to transfer data between different components.
Address Bus: It is used to transfer addresses of memory locations for the CPU to perform read/write operations in
the memory.
Control Bus: It is used to transfer control signals between various computer components.

Input and
CPU Memory Output

Control bus
System bus

Address bus

Data bus

Fig 1.7: System Bus

The data bus, address bus, and control bus together constitute the system bus. Fig 1.7 depicts the flow within the
system bus. Data entered from an input device is stored in the main memory. The CPU then accesses this data using a
data bus. The address of the memory location from where data will be accessed is communicated via the address bus.

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