[Manishkumar12]

x86 and x64 are the names of the cpu architectures. There is more to a cpu architecture than just the number of bits per register.

x64 takes is name because the jump to 64 bits is the biggest change in the architecture from x86, but that jump is far from the only change.

x86 gets it's name from the venerable 8086 processor and family, which included 80286, 80368, 486, etc. At the time that x86 became established as a name for the architecture, 32 bits per register was not considered an important enough feature to justify building it into the name.