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Pointer Addressing

Created by: s_vb at: 6/19/2012 11:52 AM (5 Replies)

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6/19/2012 11:52 AM	Rate (0)
s_vb Bronze Member Joined: 10/24/2011 Last visit: 3/9/2023 Posts: 257 Rating: (1)	Dear Sir, I am using this reference program for studying pointer addressing.. //************************************************************************************************// P##Measuring_values //Address of ANY-Pointer LAR1 //Load the pointer in AR1 L B [AR1,P#1.0] //Check the type of data L 8 //Load the code of REAL (16#08) ==I JC calc //Jump, if the type of data = REAL NOP 0 //Instructions, if type data <> REAL CLR //VKE = 0 SAVE //BIE = 0 L L#-1 //Load the value, which is not apply T #Sum T #Average_value BEU //Interrupt, if the REAL-value is not apply BE calc: NOP 0 //Instructions if type of data = REAL L W [AR1,P#2.0] //Load the repeat factor in accu 1 T #quantity //Transfer to TEMP-variable for count of looping L W [AR1,P#4.0] //Load the DB-No. T #DB_No //Transfer to TEMP-variable OPN DB [#DB_No] //Run time error, if the DB is not exist L D [AR1,P#6.0] //Load the area pointer in accu 1 LAR1 L 0.000000e+000 //Load 0 in accu 1 L #quantity //Load the count value in accu 1 turn: T #Loop_count //Transfer to counter of looping (TEMP-variable) TAK //Sum in accu 1 L D [AR1,P#0.0] //Load the field component in accu 1 +R //REAL-Addition to Sum in accu 1 +AR1 P#4.0 //Incrementation of 4 bytes in AR1 L #Loop_count //Count of looping in accu 1, and sum in accu 2 LOOP turn //Decrementation of count of looping TAK //Change sum to accu 1 T #Sum //Transfer to output of sum L #quantity //Load the quantity in accu 1 DTR //Convert the type of data into REAL /R //Calculation of average value and load to accu 1 T #Average_value //Transfer to output of average value SET //Set BIE-Bit to 1 SAVE //**********************************************************************************************// In above code P##Measuring_values //Address of ANY-Pointer LAR1 //Load the pointer in AR1 L B [AR1,P#1.0] //Check the type of data (How this instruction is working)** L 8 //Load the code of REAL (16#08) ==I JC calc Please explain me this instruction. Thanks Shailesh V. Bangale

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6/19/2012 12:27 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 7/10/2025 Posts: 1561 Rating: (540)	Well what the code is doing is accessing the second byte of the ANY pointer, which is the data type. The address register is setup to point to the start of the ANY pointer. The P#1.0 is basically saying access the address pointed to by address register 1 + and fixed offset of 1. This data is then converted into a byte and loaded into accumulator 1. The type is then tested to see if it points to a REAL type (value = 8).
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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6/19/2012 5:38 PM	Rate (0)
manmeet Gold Member Joined: 1/3/2006 Last visit: 2/19/2024 Posts: 726 Rating: (71)	Hi, To understand ANY structure read this /tf/WW/en/Posts/45921

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6/20/2012 7:10 AM	Rate (0)
MM1234 Posts: 270 Rating: (53)	Dear s_vb, I will refer to the last three lines of code you mentioned (that include the part you don't understand). First one, L P##Measuring_valuesprepares the pointer to Measuring_values and then the second one LAR1 loads it into address register AR1. That's pretty clear, I think. What L B[AR1, P#1.1] does is simply following: You load byte into accufrom the address specified in AR1 (that's start of Measuring_values) increased by 1 byte and 1 bit. I can't tell you what exact reason is behind this particular syntax, maybe it's more effective in terms of performance, maybe it's just because it makes the code much simpler in terms of # lines, so it's easier to see what it means. I hope this clears some confusion.
MM1234 Posts: 270 Rating: (53)
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6/20/2012 7:44 AM	Rate (1)
Aret Posts: 2348 Rating: (265)	L B [AR1,P#1.1] //Check the type of data I believe it's just an error. You can't load half of byte 0 and another half from byte 1, indirect addressing clearly restricts it. So this line should look like L B [AR1,P#1.0] //Check the type of data Next - REAL code is really b#16#08 so next line should be L 8 // in your code you have L 9 Everything else looks good at first glance.
Aret Posts: 2348 Rating: (265)	Last edited by: Aret at: 6/20/2012 7:46 AM
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6/20/2012 7:55 AM	Rate (0)
MM1234 Posts: 270 Rating: (53)	That's very good point Aret, I didn't even know that it's not possible, not mentioning the fact that I missed what kind of nonsense it is.
MM1234 Posts: 270 Rating: (53)
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