VHDL code for register, to use in a binary multiplication circuit

[Altera_Forum]

I wrote a piece a VHDL code for a register (to make a shift register circuit) in a binary multiplication circuit. Once I analyzed it in Quartus II several syntax errors were displayed. 

This is my code:  ENTITY memory ISPORT (can_load, can_shift, can_ad, sb_input, ab_input, UserInput : IN BIT;  Out_Bit, Z : OUT BIT); END memory;   ARCHITECTURE logic OF memory IS SIGNAL State: BIT := '0';   BEGIN    IF (can_load = '1') THEN   State <= UserInput;   ELSE   IF (can_ad = '1') THEN Z <= State; --Z is the output that goes to the 4 bit adder   State <= ab_input;  END IF;   IF (can_shift = '1') THEN   Out_Bit <= State;   State <= sb_input;   END IF;   END IF; END logic;  This are the error messages:  Info: ******************************************************************* Info: Running Quartus II 64-Bit Analysis & Synthesis Info: Version 14.0.0 Build 200 06/17/2014 SJ Web Edition Info: Processing started: Sun Oct 19 16:28:22 2014 Info: Version 14.0.0 Build 200 06/17/2014 SJ Web Edition Info: Processing started: Sun Oct 19 16:28:22 2014 Info: Command: quartus_map --read_settings_files=on --write_settings_files=off memory -c memory Warning (20028): Parallel compilation is not licensed and has been disabled Error (10500): VHDL syntax error at memory.vhd(9) near text "IF"; expecting "end", or "(", or an identifier ("if" is a reserved keyword), or a concurrent statement Error (10500): VHDL syntax error at memory.vhd(9) near text "THEN"; expecting "<=" Error (10500): VHDL syntax error at memory.vhd(11) near text "ELSE"; expecting "end", or "(", or an identifier ("else" is a reserved keyword), or a concurrent statement Error (10500): VHDL syntax error at memory.vhd(12) near text "THEN"; expecting "<=" Error (10500): VHDL syntax error at memory.vhd(15) near text "IF"; expecting ";", or an identifier ("if" is a reserved keyword), or "architecture" Error (10500): VHDL syntax error at memory.vhd(16) near text "THEN"; expecting "<=" Error (10500): VHDL syntax error at memory.vhd(19) near text "IF"; expecting ";", or an identifier ("if" is a reserved keyword), or "architecture" Info (12021): Found 0 design units, including 0 entities, in source file memory.vhd I have already checked several books for the correct syntax, and code examples and yet I cannot find where's my mistake. I also tried to take away the parentheses in sections like this:  IF (can_load = '1') THEN  having something like this:  IF can_load = '1' THEN  but I ended up with most of the same syntax errors.  I'd appreciate any help to solve this issue. Thank you very much.

[Altera_Forum]

conditional assigment with "if" are only valid inside a process: 

 process( here write the sensitivity list begin  if( ....  Anyway, your code doesn't look good. You are using vhdl like a C program.

[Altera_Forum]

When you put the code in a process, the code you have does not actually describe a register - you need a clock input. and then all the code needs to be wrapped inside: 

 if rising_edge(clk) then

[Altera_Forum]

--- Quote Start ---  When you put the code in a process, the code you have does not actually describe a register - you need a clock input. and then all the code needs to be wrapped inside:  if rising_edge(clk) then  --- Quote End ---    Thank you, I just did it and it did work :)

[Altera_Forum]

Thank you, I put it inside a clock process and it did work.  

 I am new to VHDL, so I would really appreciate if you could share some link to an example of a well written VHDL code. I know I do write as if I were making a C program, because I've only coded microcontrollers in C.

[Altera_Forum]

This book is highly recommended: http://www.amazon.co.uk/designers-guide-vhdl-systems-silicon/dp/0120887851/ref=sr_1_1?ie=utf8&qid=1413965590&sr=8-1&keywords=designers+guide+to+vhdl 

 but any good tutorial you can find on google should tell you how to code the basics.

[Altera_Forum]

--- Quote Start ---  This book is highly recommended: http://www.amazon.co.uk/designers-guide-vhdl-systems-silicon/dp/0120887851/ref=sr_1_1?ie=utf8&qid=1413965590&sr=8-1&keywords=designers+guide+to+vhdl  but any good tutorial you can find on google should tell you how to code the basics.  --- Quote End ---    Thank you so much :)