About most significant bit

#1

I didn’t get the point that why if MSB is 1 then the number will be negative and if the MSB is 0 then then the number will be positive.

#2

The MSB isn’t for denoting positive or negative. Only when you write the number in a certain bit length like say, if you agree to write all numbers in 4 bit length, then 4th bit from left represent the sign of number. Usually in computer integer is represented as 32 bit, so 32th bit represent sign of it.

you can refer to this for more :https://www.cybercomputing.co.uk/Languages/Languages/Low_level/negativeBinary.html