Ch. 2 Flashcards
What does the word addressable means?
The term, “addressable,” means that a particular byte can be retrieved according to its location in memory.
What is the smallest possible addressable unit of
computer storage?
A byte is the smallest possible addressable unit of
computer storage.
What are disadvantage of signed magnitude?
It requires complicated computer hardware.
And it allows two different representations for zero: positive zero and negative zero.
How do you express a value in two’s complement representation?
To express a value in two’s complement representation:
– If the number is positive, just convert it to binary and you’re done.
– If the number is negative, find the one’s complement of the number and then add 1.
What is the rule for detecting an overflow with two’s complement representation?
Rule for detecting signed two’s complement overflow: When the “carry in” and the “carry out” of the sign bit differ, overflow has occurred. If the carry into the sign bit equals the carry out of the sign bit, no overflow has occurred.
True or False: The signed magnitude, one’s complement, and two’s complement representation that we have just presented deal with signed integer values only.
True
What is the length in bits of a floating point number with the Simple Model? What is the size of the exponent field? The significand field?
– A floating-point number is 14 bits in length
– The exponent field is 5 bits
– The significand field is 8 bits
In floating point representation, with the Simple Model, what consist the process of normalization?
It’s a rule that the first digit of the significand must be 1, with no ones to the left of the radix point. (0.1XXXXX)
What is biased exponent ?
A bias is a number that is approximately midway in the range of values expressible by the exponent. We subtract the bias from the value in the exponent to determine its true value.
What is the biased exponent for the Simple Model?
In our case, we have a 5-bit exponent. We will use 16 for our bias. This is called excess-16 representation.
• In our model, exponent values less than 16 are negative, representing fractional numbers.
What consist of the IEEE-754 single precision floating point standard? What size is the exponent? The significand?
The IEEE 754 single precision floating point standard uses an 8-bit exponent (with a bias of 127) and a 23-bit significand.
What consist of the IEEE-754 double precision floating point standard? What size is the exponent? The significand?
The IEEE-754 double precision standard uses an 11-bit exponent (with a bias of 1023) and a 52-bit significand.
What is the difference between IEEE-754 and the Simple Model?
In both the IEEE single-precision and double- precision floating-point standard, the significant has an implied 1 to the LEFT of the radix point. The format for a significand using the IEEE format is: 1.xxx…
What are the special values for IEEE-754 single and double precision?
Using the IEEE-754 single precision floating point standard:
– An exponent of 255 indicates a special value.
• If the significand is zero, the value is infinity.
• If the significand is nonzero, the value is NaN, “not a number,” often used to flag an error condition.
Using the double precision standard:
– The “special” exponent value for a double precision number is 2047, instead of the 255 used by the single precision standard.
Why programmers should avoid testing a floating-point value for equality to zero?
Both the 14-bit model that we have presented and the IEEE-754 floating point standard allow two representations for zero.
– Zero is indicated by all zeros in the exponent and the significand, but the sign bit can be either 0 or 1
