Difference between RAM & ROM

RAM	ROM
Random Access Memory	Read Only memory
User can read & write into it	User can only read from it
For any type of processing, user must store program & data into RAM	Manufacturer stores instruction into ROM permanently
Temporary or volatile memory	Permanent or non-volatile memory

Cache Memory or High Speed Buffer

Cache Memory

• Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.

• Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.

• CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache.

• The amount of cache memory has a tremendous impact on the computer's speed.

Secondary Memory or Secondary Storage Devices

Secondary Memory

Ø Nonvolatile

Ø Slow compared to primary memory

Ø Less costly & high capacity

Categorizing Storage Devices

• The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.

• Storage devices hold data, even when the computer is turned off.

• The two primary storage technologies are magnetic and optical.

• Magnetic storage are:

-Diskettes (floppy disks)

-Hard disks

• Optical storage are:

-Compact Disk Read-Only Memory (CD-ROM)

-Digital Video Disk Read-Only Memory (DVD- ROM)

Comparison of primary & secondary memory

Characteristics	Primary	Secondary
Location with respect to the CPU	Directly accessible	Indirectly accessible
Cost	More expensive	Less expensive
Capacity	Lower than secondary memory	Several thousand times higher than primary
Means of storing information	Semiconductor chips	Magnetic and optical

A Program that will Find the Two Numbers Addition

First Method:

#include
Void main ()
{
int a, b, sum;
sum = a + b
printf ("Enter Two Numbers :\n");
scanf ("%d %d\n", & a, & b);
printf ("Sum of two Numbers: \n", sum);
}

Second Method:

#include
int main ()
{
int a, b, sum;
sum = a + b
printf ("Enter First Input:\n");
scanf ("%d\n", & a);
printf ("Enter Second Input:\n");
scanf ("%d\n", & b);
printf ("Sum is: \n", sum);
}

A Program that will Count Temperature From Celcius to Farenite

#include
void main ()
{
float cel, faren;
printf ("Enter value in celcius:\n");
scanf ("%f\n", &cel);
faren = 18*cel+32;
printf ("Farenite Result is :\n", faren);
}