CPU is an acronym for Central Processing Unit.

Mp will stand for the primary Memory, which is often called RAM.
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Primary Memory, Mp, is the desktop of the computer.  
A program such as WordPerfect or Microsoft Word or Netscape must
be loaded into Mp from Ms before it can be executed by the computer.

Analogy:  You must get the recipe out of your recipe box and place
          it on your kitchen counter before you can start making the
          brownies or beef ole.

Ms is Secondary Memory also known as Secondary Storage.
      -         -

Ms is like your desk drawers or your file cabinets or your bookshelves.
You have to get your journal out of the file cabinet or desk drawer,
before you can read it and write more information to it.

Nobody climbs into their desk drawer or file cabinet drawer to work
on their journal or paper or grading.   They move it from the 
secondary Memory (Ms) onto the desktop, their Mp Primary Memory.

The paper you are working on is the data.  The wordperfect or microsoft
word program you are using for the word processing is the program.

Both the data and the program have to be in RAM, i.e. in Mp, before
the CPU can become a word processor for you.

The data (your paper) and the software (Microsoft Word) are both stored
on Ms, which is magnetic secondary storage, such as hard drive or flash
drive or diskette.

The ENIAC computer had 18,000 vacuum tubes and weighed about 30 tons.

The ABC computer was developed by Iowa State College physics professor
John Vincent Atanasoff and his graduate assistant Clifford Berry. ABC
stands for Atanasoff/Berry Computer.
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The ABC computer was a special purpose electronic digital computer
for solving mathematically intensive physics equations.

John Mauchly read Atanasoff's paper, saw his ABC computer on a visit
to Ames, Iowa in the late 30s or early 40s.  When he developed the
ENIAC computer for use in World War II by the USA in calculating
ballistic firing tables, he did NOT give credit to Atanasoff for
the scientific breakthroughs and the ABC machine he shared freely with 
him.  

A 10 year long court battle decades later called Honeywell versus Sperry 
Rand decided that the electronic digital computer was invented by 
Atanasoff at Iowa State College in Ames in the 1930s.   Mauchly and
Eckert's government funded ENIAC computer, it was decided, had been
derived from Atanasoff's ideas.