Tutorial By Namitha

               In the microprogrammed control units all the control signals associated with microoperations are stored in special memory called control memory .           Set of control signals that cause microoperations to occur is called microinstructions .           Micro-programmed control unit can be classified into two types based on the type of Control Word(microinstructions) stored in the Control Memory .  Horizontal micro-programmed control unit   Vertical micro-programmed control unit In  Horizontal micro-programmed  control unit, the control signals are represented in the decoded binary format .                     ‘n ’ control signals require n bit encoding i.e., 1 bit/CS .  In  Vertical micro-programmed   control unit, the control signals are repres...

A digital computer consists of CPU , a memory and I/O devices . CPU can be classified into two distinct but interactive fu nctional units    1)  Processing section (Processor)                               2) Control Section Microprogram sequencer is a convenient element for constructing a microprogram control for CPU .  Microprogrammed Computer consists of a  Memory unit ,two processor unit , a microprogram sequencer ,a control memory and few other digital functions . The memory unit stores the instructions and data supplied by the user through an input device .

A microprogram control unit consists of two parts : 1 ) Control Memory that stores the microinstructions 2) Associated circuits that control the generation of the next address . The address generation part is sometimes called a microprogram sequencer ,since it sequences the microinstructions in control memory .   T ypical sequencer provides the following address-sequencing capabilities : 1.Increments the present address for control memory .    Sequential access: The content of address register of the control memory (CAR) is    incremented after execution of each micro-instruction . 2. Branches to an address as specified by the address field of the microinstruction. 3 . Branches to a given address if a specified status bit equal to 1. 4.Transfer control to a new address as specified by an external source .   The external address transfers control to the first microinstruction in a microprogram . 5 .Support subroutine call ...

Control Memory In a micro-program control, the control variables that initiate micro-operations are stored in memory called control memory. •The control memory is a ROM, since the control sequence is permanent and needs no alteration. Micro instructions The word stored in the control memory are micro-instructions. Each micro-instruction specifies one or more micro-operations for the components in the system. 

Normalisationis a process of organizing the data in database to avoid data redundancyand anomalies . We have different levels of normal forms 1st,2nd, 3rd , BCNF ,4th,5th etc . A relation is always specified with its highest normalization level . First Normal Form defines that all the attributes in a relation must have atomic values . Second Normal Form is based on the concept of fully functional dependency . To be in second normal form, a relation must be in First Normal Form and every non-prim attributes are fully functionally dependent on any of the candidate keys. A relation is in 3rd normal form , 1)It must be in 2NF 2)Nonprime attributes should not be transitively dependent on candidate keys. For a relation to be in Boyce-CoddNormal Form (BCNF  or 3.5 NF) , 1.It should be in theThird Normal Form. 2.And, for any dependency X→ Y, X must be asuper key. Stronger version of 3NF .

A minimal cover of a set of FDs F is a minimal set of functional dependencies F min  that is equivalent to F. There can be many such minimal covers for a set of functional dependencies F. Steps to derive  minimal cover for  a FD set . 1)Right Hand Side (RHS) of all FDs should be single attribute . 2)Eliminate redundant functional dependencies if any . Given relation R(A,B,C)    and      FDs : {  AB -> C, C -> A }    FDmin ={AB à C}   ,here C-->A is   redundant dependency  3)Remove redundant attribute on LHS if any .  Consider  FD ,  AB -> C              If AB+ = A+  we can say B is redundant  then reduce to  A à C              If AB+ =B+ we can say A is redundant then reduce to B à C