How Switch case Statement Implemented or works internally?

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It’s actually up to the compiler how a switch statement is realized in code.

However, my understanding is that when it’s suitable (that is, relatively dense cases), a jump table is used.

That would mean that something like:

switch(i) {
  case 0: doZero(); break;
  case 1: doOne();
  case 2: doTwo(); break;
  default: doDefault();
}

Would end up getting compiled to something like (horrible pseudo-assembler, but it should be clear, I hope).

load i into REG
compare REG to 2
if greater, jmp to DEFAULT
compare REG to 0
if less jmp to DEFAULT
jmp to table[REG]
data table
  ZERO
  ONE
  TWO
end data
ZERO: call doZero
jmp END
ONE: call doOne
TWO: call doTwo
jmp END
DEFAULT: call doDefault
END:

If that’s not the case, there are other possible implementations that allow for some extent of “better than a a sequence of conditionals”.

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