Simply Explained

Introduction to Computer Architecture

  • Computers naturally use binary numbers.
  • A binary number consists of 8 bits.
  • 8 bits make up one byte.
  • Computers group bits by the powers of 2.
  • Modern computers are 32 bit or 64 bit which means that they deal naturally with numbers of this size.
  • This natural unit of 32 or 64 bits is called a word.
  • 1 hex digit is 4 bits.
  • 1 binary digit is 1 bit.
  • An n-bit architecture generally supports n-bit numbers.
  • A word is the natural unit of data used by a particular processor design.
  • A pointer stores a reference to another value. Pointers are numbers too.
  • Word size is also the address space on the computer.
  • A computer said to be 32 bit usually allows 32-bit memory addresses. This allows one memory address to be efficiently stored in one word.


  • An adder is a digital circuit that performs addition of numbers.
  • The half adder adds two input single binary digits or bits and generates a carry and a sum. The input variables are called augend and addend bits. The output variables are sum and carry.
  • A full adder adds two binary numbers and accounts for both carry in as well as carry out.
  • A one-bit full adder adds three one bit numbers, A, B, and Cin. Where A and B are the operands and Cin is the bit carried in from the previous stage.
  • A circuit created using multiple full adders to add n-bit numbers is called a ripple carry adder. Each full adder inputs a Cin which is the Cout of the previous adder.


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