diff --git a/common/common.asm b/common/common.asm
index 285c511..8094e37 100644
--- a/common/common.asm
+++ b/common/common.asm
@@ -977,14 +977,23 @@ _CPR	.(		; CPR pq		0c pq		Rp <- Rq	- copy register
 
 _INILS	.(		; common initialization for LDI and SVI
 	JSR _CPYI1	; copy q to I1
+	LDA _I1+3	; check for negative offsets
+	BMI _1
 	CLC		; add the allocated memory offset
-	LDA _ARL
+	LDA _ARLL
 	ADC _I1+1
 	STA _I1+1
-	LDA _ARH
+	LDA _ARLH
 	ADC _I1+2
 	STA _I1+2
-	RTS
+	CMP _ARUH	; compare against upper limit
+	BCC _2		; for sure less
+	BNE _1		; not equal, must be more
+	LDA _I1+1
+	CMP _ARUL
+	BCC _2		; for sure less
+_1	BRK		; accessing out of bounds, abort and call exception handler (TODO)
+_2	RTS
 .)
 
 _LDI	.(		; LDI pq		0d pq		Rp <- (Rq:bbcc)	- load indirect from memory
diff --git a/common/common.h b/common/common.h
index f08db35..c1ac676 100644
--- a/common/common.h
+++ b/common/common.h
@@ -88,13 +88,12 @@ _F_N	=  32				; if Rr < 0.0 (after TST)
 _F_O	=  64				; if overflow (after arithmetic operations)
 _F_U	= 128				; if underflow (after arithmetic operations)
 
-; register I7 maintains locations of code and allocated memory
-_CRL	= _I7				; code low and high bytes
-_CRH	= _CRL + 1
-_ARL	= _CRH + 1			; allocated low and high bytes
-_ARH	= _ARL + 1
-_CR	= _CRL				; code memory address
-_AR	= _ARL				; allocated memory address
+; register I7 maintains locations of allocated memory
+_ARLL	= _I7				; allocated low and high bytes
+_ARLH	= _ARLL + 1
+_ARUL	= _ARLH + 1			; allocated upper limit
+_ARUH	= _ARUL + 1
+_AR	= _ARLL				; allocated memory address
 
 ; register I8 is reserved for future use, e.g. context switching
 
diff --git a/common/page6.src b/common/page6.src
index 1431939..548c83e 100644
--- a/common/page6.src
+++ b/common/page6.src
@@ -2,13 +2,13 @@
 #include "macros.h"
 #include "globals.h"
 
-	* = $1000	; any address outside of page zero is okay
+	* = $1000		; any address outside of page zero is okay
 
 CODE(DEMO)
 START
 	CMN
 	SET(R0, 9.4662)
-	SET(R1, 2)
+	SET(R1, 5)
 	LDI(R7, R1)
 	MUL(R7, R7, R7)
 	SVI(R1, R0)
diff --git a/emulator/main.c b/emulator/main.c
index d4ddc67..1111066 100644
--- a/emulator/main.c
+++ b/emulator/main.c
@@ -17,13 +17,12 @@
 #define _F	_PCH + 1	/* flags */
 #define _PC	_PCL		/* program counter */
 
-/* register I7 maintains locations of code and allocated memory */
-#define _CRL	_I7				/* code low and high bytes */
-#define _CRH	_CRL + 1
-#define _ARL	_CRH + 1			/* allocated low and high bytes */
-#define _ARH	_ARL + 1
-#define _CR	_CRL				/* code memory address */
-#define _AR	_ARL				/* allocated memory address */
+/* register I7 maintains locations of allocated */
+#define _ARLL	_I7				/* allocated low and high bytes */
+#define _ARLH	_ARLL + 1
+#define _ARUL	_ARLH + 1			/* allocated upper limit */
+#define _ARUH	_ARUL + 1
+#define _AR	_ARLL				/* allocated memory address */
 
 /* section modifiers */
 #define _SM_FXD	0x01
@@ -91,8 +90,8 @@ int main() {
 					/* offset the starting address */
 					entity += index;
 					/* save the starting address */
-					memory[_CRL] = entity & 0xff;
-					memory[_CRH] = entity >> 8;
+					memory[_PCL] = entity & 0xff;
+					memory[_PCH] = entity >> 8;
 					/* advance to the end of the section */
 					index += length;
 				}
@@ -102,18 +101,18 @@ int main() {
 				/* entity is the length of zeroed data, length is the length of preset data */
 				if (fread(memory + index, length, 1, stdin)) {
 					/* save the start of the data */
-					memory[_ARL] = index & 0xff;
-					memory[_ARH] = index >> 8;
+					memory[_ARLL] = index & 0xff;
+					memory[_ARLH] = index >> 8;
 					/* advance to the end of the section */
 					index += entity + length;
+					/* save the end of the data */
+					memory[_ARUL] = index & 0xff;
+					memory[_ARUH] = index >> 8;
 				}
 				break;
 		}
 	}
 
-	memory[_PCL] = 	memory[_CRL];
-	memory[_PCH] = 	memory[_CRH];
-
 	hookexternal(hook);
 
 	reset6502();