Why are binary numbers sometimes written with one or more leading zeros that don't change the number (quantity) represented?

Binary numbers like '0110', or '00100101' are seen very often in all contexts. What are the leading (left hand side) zeroes for? Why did the writer not write '110' and '100101', respectively?

Leading zeroes in binary usually indicate the bit length of the data type. For example, the number 110 represented in a 4 bit data type would be 0110. Even if there is no data type specified, it's sometimes common to pad your binary numbers to the next power of 2. For example, 10111 of size 5 should be padded to 8 $$(2^3)$$ as 00010111
Depend on context, so, I bring one small example: if we consider $$3$$-bit field, then $$110$$ is negative in $$2$$'s complement and equal $$-2$$, while in $$4$$-bit field $$0110$$ is positive and equal $$6$$ in same $$2$$'s complement.
• Yes. In $2$'s complement all binary code with leading bit $1$ is negative. Apr 11 at 17:07