Decimal Numbers
//The position of each digit in a weighted number system is assigned a weight based on the base or radix of the system. The radix of decimal numbers is ten, because only ten symbols (0 through 9) are used to represent any number.
// The column weights of decimal numbers are powers of ten that increase from right to left beginning with 100 =1:
// For fractional decimal numbers, the column weights are negative powers of ten that decrease from left to right:
//Decimal numbers can be expressed as the sum of the products of each digit times the column value for that digit. Thus, the number 9240 can be expressed as
//Express the number 480.52 as the sum of values of each digit.
Binary Numbers
//For digital systems, the binary number system is used. Binary has a radix of two and uses the digits 0 and 1 to represent quantities.
// The column weights of binary numbers are powers of two that increase from right to left beginning with 20 =1:
// For fractional binary numbers, the column weights are negative powers of two that decrease from left to right:
//A binary counting sequence for numbers from zero to fifteen is shown.
//Notice the pattern of zeros and ones in each column.
//Digital counters frequently have this same pattern of digits:
Binary Conversions
//The decimal equivalent of a binary number can be determined by adding the column values of all of the bits that are 1 and discarding all of the bits that are 0.
//Convert the binary number 100101.01 to decimal.
//Start by writing the column weights; then add the weights that correspond to each 1 in the number.
//You can convert a decimal whole number to binary by reversing the procedure. Write the decimal weight of each column and place 1’s in the columns that sum to the decimal number.
//Convert the decimal number 49 to binary.
//The column weights double in each position to the right. Write down column weights until the last number is larger than the one you want to convert.
//You can convert a decimal fraction to binary by repeatedly multiplying the fractional results of successive multiplications by 2. The carries form the binary number.
//Convert the decimal fraction 0.188 to binary by repeatedly multiplying the fractional results by 2.
//You can convert decimal to any other base by repeatedly dividing by the base. For binary, repeatedly divide by 2:
//Convert the decimal number 49 to binary by repeatedly dividing by 2.
//You can do this by “reverse division” and the answer will read from left to right. Put quotients to the left and remainders on top.
Binary Addition
//The rules for binary addition are
//When an input carry = 1 due to a previous result, the rules are
//Add the binary numbers 00111 and 10101 and show the equivalent decimal addition.
Binary Subtraction
//Subtract the binary number 00111 from 10101 and show the equivalent decimal subtraction.
1’s Complement
//The 1’s complement of a binary number is just the inverse of the digits. To form the 1’s complement, change all 0’s to 1’s and all 1’s to 0’s.
//For example, the 1’s complement of 11001010 is
//In digital circuits, the 1’s complement is formed by using inverters:
2’s Complement
//The 2’s complement of a binary number is found by adding 1 to the LSB of the 1’s complement.
//Recall that the 1’s complement of 11001010 is
//To form the 2’s complement, add 1:
Signed Binary Numbers
//There are several ways to represent signed binary numbers. In all cases, the MSB in a signed number is the sign bit, that tells you if the number is positive or negative.
// Computers use a modified 2’s complement for signed numbers. Positive numbers are stored in true form (with a 0 for the sign bit) and negative numbers are stored in complement form (with a 1 for the sign bit).
//For example, the positive number 58 is written using 8-bits as 00111010 (true form).
Signed Binary Numbers
//Negative numbers are written as the 2’s complement of the corresponding positive number.
//The negative number -58 is written as:
//-58 = 11000110 (complement form)
//An easy way to read a signed number that uses this notation is to assign the sign bit a column weight of -128 (for an 8-bit number). Then add the column weights for the 1’s.
//Assuming that the sign bit = -128, show that 11000110 = -58 as a 2’s complement signed number:
//Column weights: -128 64 32 16 8 4 2 1.
Floating Point Numbers
//Floating point notation is capable of representing very large or small numbers by using a form of scientific notation. A 32-bit single precision number is illustrated.
//Express the speed of light, c, in single precision floating point notation. (c = 0.2998 x 109)
Arithmetic Operations with Signed Numbers
//Using the signed number notation with negative numbers in 2’s complement form simplifies addition and subtraction of signed numbers.
//Rules for addition: Add the two signed numbers. Discard any final carries. The result is in signed form.
Examples:
//Note that if the number of bits required for the answer is exceeded, overflow will occur. This occurs only if both numbers have the same sign. The overflow will be indicated by an incorrect sign bit.
//Rules for subtraction: 2’s complement the subtrahend and add the numbers. Discard any final carries. The result is in signed form.
//Repeat the examples done previously, but subtract:
//2’s complement subtrahend and add:
Hexadecimal Numbers
//Hexadecimal uses sixteen characters to represent numbers: the numbers 0 through 9 and the alphabetic characters A through F.
// Large binary number can easily be converted to hexadecimal by grouping bits 4 at a time and writing the equivalent hexadecimal character.
//Express 1001 0110 0000 11102 in hexadecimal:
//Group the binary number by 4-bits starting from the right. Thus, 960E
//Hexadecimal is a weighted number system. The column weights are powers of 16, which increase from right to left.
//Express 1A2F16 in decimal.
//Start by writing the column weights:
4096 256 16 1
Octal Numbers
//Octal uses eight characters the numbers 0 through 7 to represent numbers. There is no 8 or 9 character in octal.
// Binary number can easily be converted to octal by grouping bits 3 at a time and writing the equivalent octal character for each group.
//Express 1 001 011 000 001 1102 in octal:
//Group the binary number by 3-bits starting from the right. Thus, 1130168
Octal Numbers
//Octal is also a weighted number system. The column weights are powers of 8, which increase from right to left.
//Express 37028 in decimal.
//Start by writing the column weights:
512 64 8 1