Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved. 

Mechanical analog computers started appearing in the first century and were later used in the medieval era for astronomical calculations. In World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs). 

Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space. Computers are small enough to fit into mobile devices, and mobile computers can be powered by small batteries. Personal computers in their various forms are icons of the Information Age and are generally considered as "computers". However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous.
What does CPU stand for?
Are peripheral devices useful?
When did the first computers start appearing?
How big were the first digital computers?
How were analog computers used in WWII?
such as?
Are modern computers more efficient than early computers?
What has to accompany the processing unit?
What does the processing unit do?
What were computers used for in the medieval era?
Did original digital computers use a lot of power?
How much?
Are computers found in a lot of contemporary items?
such as?
and?
and?
central processing unit
Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU)
yes
Peripheral devices allow information to be retrieved from an external source, 
the first century
Mechanical analog computers started appearing in the first century 
The size of a large room
Originally they were the size of a large room,
in specialized military applications
n World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming
calculating torpedo aiming
In World War II, mechanical analog computers were used for specialized military applications such as calculating torpedo aiming.
yes
Modern computers based on integrated circuits are millions to billions of times more capable than the early machines
memory
Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory
carries out arithmetic and logic operations
The processing element carries out arithmetic and logic operations
astronomical calculations
Mechanical analog computers started appearing in the first century and were later used in the medieval era for astronomical calculations.
yes
Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs). 
as much as several hundred modern personal computers
Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs). 
yes
However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous.
MP3 players
However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous.
fighter aircraft
However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous
industrial robots
However, the embedded computers found in many devices from MP3 players to fighter aircraft and from electronic toys to industrial robots are the most numerous