Binary code is a system of encoding information using only TWO symbols, ONES and zeros. The term 'about half of binary code' refers to the fact that half of the symbols used in binary code are ONES, while the other half are zeros. The crossword solutions for this term are ONES (4 letters), ZERO (4 letters), ONE (3 letters), TEN (3 letters), and TWO (3 letters). These words represent the symbols used in binary code, with ONES and ZERO representing the TWO symbols, ONE representing the number ONE, TEN representing the number TEN, and TWO representing the number TWO.