diff --git a/README.md b/README.md
index e31b9df..efcf28c 100644
--- a/README.md
+++ b/README.md
@@ -643,10 +643,39 @@ Abort assembly if any of the expressions is false.
 
 Seed the random number generator used by the RND() function.  If this is not used, the random number generator is seeded based on the current time and so each build of a program using `RND()` will be different.
 
+
 `ASM <str>`
 
 Assemble the supplied assembly language string.  For example `ASM "LDA #&41"`.
 
+
+`DEFINE <var-name> <expr>`
+
+Evaluates `<var-name>` as the name of a variable to define with value `<expr>`. The `<var-name>` expressison must be a string, for example `DEFINE "addr" &70`. It is not possible to re-assign variables.
+
+This must be used instead of `=` when the variable name needs to be generated dynamically such as from macro arguments, for example:
+
+```
+    MACRO VIA name, base_addr
+      DEFINE name, addr
+      DEFINE name + "_IOR_B", base_addr
+      DEFINE name + "_IOR_A", base_addr + 1
+      DEFINE name + "_DDR_B", base_addr + 2
+      DEFINE name + "_DDR_A", base_addr + 3
+      ; ...
+      ; ...
+    ENDMACRO
+
+    VIA SYSVIA, &FE40
+    VIA USERVIA, &FE60
+```
+
+
+`ASSIGN <var-name> <expr>`
+
+Does the same thing as `DEFINE <var-name> <expr>` except that it can be used to change the value of a variable.
+
+
 ## 7. TIPS AND TRICKS
 
 BeebAsm's approach of treating memory as a canvas which can be written to, saved, and rewritten if desired makes it very easy to create certain types of applications.
diff --git a/src/commands.cpp b/src/commands.cpp
index c53a8a2..18ed00f 100644
--- a/src/commands.cpp
+++ b/src/commands.cpp
@@ -82,7 +82,9 @@ const LineParser::Token	LineParser::m_gaTokenTable[] =
 	{ "ERROR",		&LineParser::HandleError,				0 },
 	{ "COPYBLOCK",	&LineParser::HandleCopyBlock,			0 },
 	{ "RANDOMIZE",  &LineParser::HandleRandomize,			0 },
-	{ "ASM",		&LineParser::HandleAsm,					0 }
+	{ "ASM",		&LineParser::HandleAsm,					0 },
+	{ "DEFINE",		&LineParser::HandleDefine,				0 },
+	{ "ASSIGN",		&LineParser::HandleAssign,				0 }
 };
 
 
@@ -1876,3 +1878,74 @@ void LineParser::HandleAsm()
 
 	parser.HandleAssembler(instruction);
 }
+
+/*************************************************************************************************/
+/**
+	LineParser::HandleDefineAssignCommon()
+	LineParser::HandleDefine()
+	LineParser::HandleAssign()
+*/
+/*************************************************************************************************/
+void LineParser::HandleDefineAssignCommon( bool bAllowRedefinition )
+{
+	string name = EvaluateExpressionAsString();
+
+	if ( name.empty() || ! ( isalpha( name[0] ) || name[0] == '_' ) )
+	{
+		throw AsmException_SyntaxError_InvalidSymbolName( m_line, m_column );
+	}
+	for (std::string::size_type i = 1, e = name.size(); i < e; ++i)
+	{
+		if ( ! ( ( isalpha( name[ i ] ) ||
+				   isdigit( name[ i ] ) ||
+				   name[ i ] == '_' ||
+				   name[ i ] == '%' ||
+				   name[ i ] == '$' ) &&
+				 name[ i - 1 ] != '%' &&
+				 name[ i - 1 ] != '$' ) )
+		{
+			throw AsmException_SyntaxError_InvalidSymbolName( m_line, m_column );
+		}
+	}
+
+	if ( ! ( AdvanceAndCheckEndOfStatement() && m_line[ m_column ] == ',' ) )
+	{
+		throw AsmException_SyntaxError_MissingComma( m_line, m_column );
+	}
+
+	++m_column;
+	if ( ! AdvanceAndCheckEndOfStatement() )
+	{
+		throw AsmException_SyntaxError_MissingValue( m_line, m_column );
+	}
+
+	Value value = EvaluateExpression();
+
+	if ( AdvanceAndCheckEndOfStatement() )
+	{
+		throw AsmException_SyntaxError_InvalidCharacter( m_line, m_column );
+	}
+
+	if ( GlobalData::Instance().IsFirstPass() )
+	{
+		if ( SymbolTable::Instance().IsSymbolDefined( name ) )
+		{
+			if ( !bAllowRedefinition )
+			{
+				throw AsmException_SyntaxError_LabelAlreadyDefined( m_line, m_column );
+			}
+			SymbolTable::Instance().RemoveSymbol( name );
+		}
+        SymbolTable::Instance().AddSymbol( name, value );
+	}
+}
+
+void LineParser::HandleDefine()
+{
+	HandleDefineAssignCommon( false );
+}
+
+void LineParser::HandleAssign()
+{
+	HandleDefineAssignCommon( true );
+}
diff --git a/src/lineparser.h b/src/lineparser.h
index 294bd13..fb393ae 100644
--- a/src/lineparser.h
+++ b/src/lineparser.h
@@ -164,6 +164,9 @@ class LineParser
 	void			HandleCopyBlock();
 	void			HandleRandomize();
 	void			HandleAsm();
+	void			HandleDefineAssignCommon( bool bAllowRedefinition );
+	void			HandleDefine();
+	void			HandleAssign();
 
 	// expression evaluating methods
 
diff --git a/test/3-directives/assign/define-variable.6502 b/test/3-directives/assign/define-variable.6502
new file mode 100644
index 0000000..994a324
--- /dev/null
+++ b/test/3-directives/assign/define-variable.6502
@@ -0,0 +1,23 @@
+\ Assign examples
+
+ASSIGN "v1",27183
+ASSERT v1 = 27183
+
+ASSIGN "v2",v1+1
+ASSERT v2 = 27184
+
+prefix = "v"
+ASSIGN prefix + "3", "A string"
+ASSERT v3 = "A string"
+
+ASSIGN "_a",1
+ASSERT _a = 1
+
+ASSIGN "a_",2
+ASSERT a_ = 2
+
+ASSIGN "a$","str"
+ASSERT a$ = "str"
+
+ASSIGN "a%",3
+ASSERT a% = 3
diff --git a/test/3-directives/assign/name-contains-bang.fail.6502 b/test/3-directives/assign/name-contains-bang.fail.6502
new file mode 100644
index 0000000..4c9e313
--- /dev/null
+++ b/test/3-directives/assign/name-contains-bang.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain general punctuation
+ASSIGN "a!b",13
diff --git a/test/3-directives/assign/name-contains-bang.fail.gold.txt b/test/3-directives/assign/name-contains-bang.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-contains-bang.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-contains-dollar.fail.6502 b/test/3-directives/assign/name-contains-dollar.fail.6502
new file mode 100644
index 0000000..76c95e9
--- /dev/null
+++ b/test/3-directives/assign/name-contains-dollar.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain a dollar
+ASSIGN "a$b",13
diff --git a/test/3-directives/assign/name-contains-dollar.fail.gold.txt b/test/3-directives/assign/name-contains-dollar.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-contains-dollar.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-contains-percent.fail.6502 b/test/3-directives/assign/name-contains-percent.fail.6502
new file mode 100644
index 0000000..c9f4bc1
--- /dev/null
+++ b/test/3-directives/assign/name-contains-percent.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain a percent
+ASSIGN "a%b",13
diff --git a/test/3-directives/assign/name-contains-percent.fail.gold.txt b/test/3-directives/assign/name-contains-percent.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-contains-percent.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-empty.fail.6502 b/test/3-directives/assign/name-empty.fail.6502
new file mode 100644
index 0000000..0912df3
--- /dev/null
+++ b/test/3-directives/assign/name-empty.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't be empty
+ASSIGN "",13
diff --git a/test/3-directives/assign/name-empty.fail.gold.txt b/test/3-directives/assign/name-empty.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-empty.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-not-string.fail.6502 b/test/3-directives/assign/name-not-string.fail.6502
new file mode 100644
index 0000000..9efed1d
--- /dev/null
+++ b/test/3-directives/assign/name-not-string.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name must be a string.
+ASSIGN 1,13
diff --git a/test/3-directives/assign/name-not-string.fail.gold.txt b/test/3-directives/assign/name-not-string.fail.gold.txt
new file mode 100644
index 0000000..ea47f95
--- /dev/null
+++ b/test/3-directives/assign/name-not-string.fail.gold.txt
@@ -0,0 +1 @@
+error: Type mismatch
diff --git a/test/3-directives/assign/name-starts-with-dollar.fail.6502 b/test/3-directives/assign/name-starts-with-dollar.fail.6502
new file mode 100644
index 0000000..bec0b26
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-dollar.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with $
+ASSIGN "$a",13
diff --git a/test/3-directives/assign/name-starts-with-dollar.fail.gold.txt b/test/3-directives/assign/name-starts-with-dollar.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-dollar.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-starts-with-number.fail.6502 b/test/3-directives/assign/name-starts-with-number.fail.6502
new file mode 100644
index 0000000..1160940
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-number.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with a number
+ASSIGN "1a",13
diff --git a/test/3-directives/assign/name-starts-with-number.fail.gold.txt b/test/3-directives/assign/name-starts-with-number.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-number.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/name-starts-with-percent.fail.6502 b/test/3-directives/assign/name-starts-with-percent.fail.6502
new file mode 100644
index 0000000..5cdf207
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-percent.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with %
+ASSIGN "%a",13
diff --git a/test/3-directives/assign/name-starts-with-percent.fail.gold.txt b/test/3-directives/assign/name-starts-with-percent.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/assign/name-starts-with-percent.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/assign/redefine.6502 b/test/3-directives/assign/redefine.6502
new file mode 100644
index 0000000..d0c9e50
--- /dev/null
+++ b/test/3-directives/assign/redefine.6502
@@ -0,0 +1,4 @@
+\ Can reassign variables
+a = 12
+ASSIGN "a",13
+ASSERT a = 13
diff --git a/test/3-directives/define/define-variable.6502 b/test/3-directives/define/define-variable.6502
new file mode 100644
index 0000000..56b6fbe
--- /dev/null
+++ b/test/3-directives/define/define-variable.6502
@@ -0,0 +1,23 @@
+\ Define examples
+
+DEFINE "v1",27183
+ASSERT v1 = 27183
+
+DEFINE "v2",v1+1
+ASSERT v2 = 27184
+
+prefix = "v"
+DEFINE prefix + "3", "A string"
+ASSERT v3 = "A string"
+
+DEFINE "_a",1
+ASSERT _a = 1
+
+DEFINE "a_",2
+ASSERT a_ = 2
+
+DEFINE "a$","str"
+ASSERT a$ = "str"
+
+DEFINE "a%",3
+ASSERT a% = 3
diff --git a/test/3-directives/define/name-contains-bang.fail.6502 b/test/3-directives/define/name-contains-bang.fail.6502
new file mode 100644
index 0000000..85317ec
--- /dev/null
+++ b/test/3-directives/define/name-contains-bang.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain general punctuation
+DEFINE "a!b",13
diff --git a/test/3-directives/define/name-contains-bang.fail.gold.txt b/test/3-directives/define/name-contains-bang.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-contains-bang.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-contains-dollar.fail.6502 b/test/3-directives/define/name-contains-dollar.fail.6502
new file mode 100644
index 0000000..4ae562d
--- /dev/null
+++ b/test/3-directives/define/name-contains-dollar.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain a dollar
+DEFINE "a$b",13
diff --git a/test/3-directives/define/name-contains-dollar.fail.gold.txt b/test/3-directives/define/name-contains-dollar.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-contains-dollar.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-contains-percent.fail.6502 b/test/3-directives/define/name-contains-percent.fail.6502
new file mode 100644
index 0000000..69cc843
--- /dev/null
+++ b/test/3-directives/define/name-contains-percent.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name cannot contain a percent
+DEFINE "a%b",13
diff --git a/test/3-directives/define/name-contains-percent.fail.gold.txt b/test/3-directives/define/name-contains-percent.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-contains-percent.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-empty.fail.6502 b/test/3-directives/define/name-empty.fail.6502
new file mode 100644
index 0000000..caa8bfb
--- /dev/null
+++ b/test/3-directives/define/name-empty.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't be empty
+DEFINE "",13
diff --git a/test/3-directives/define/name-empty.fail.gold.txt b/test/3-directives/define/name-empty.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-empty.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-not-string.fail.6502 b/test/3-directives/define/name-not-string.fail.6502
new file mode 100644
index 0000000..5c6c7c0
--- /dev/null
+++ b/test/3-directives/define/name-not-string.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name must be a string.
+DEFINE 1,13
diff --git a/test/3-directives/define/name-not-string.fail.gold.txt b/test/3-directives/define/name-not-string.fail.gold.txt
new file mode 100644
index 0000000..ea47f95
--- /dev/null
+++ b/test/3-directives/define/name-not-string.fail.gold.txt
@@ -0,0 +1 @@
+error: Type mismatch
diff --git a/test/3-directives/define/name-starts-with-dollar.fail.6502 b/test/3-directives/define/name-starts-with-dollar.fail.6502
new file mode 100644
index 0000000..7486666
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-dollar.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with $
+DEFINE "$a",13
diff --git a/test/3-directives/define/name-starts-with-dollar.fail.gold.txt b/test/3-directives/define/name-starts-with-dollar.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-dollar.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-starts-with-number.fail.6502 b/test/3-directives/define/name-starts-with-number.fail.6502
new file mode 100644
index 0000000..00758f0
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-number.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with a number
+DEFINE "1a",13
diff --git a/test/3-directives/define/name-starts-with-number.fail.gold.txt b/test/3-directives/define/name-starts-with-number.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-number.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/name-starts-with-percent.fail.6502 b/test/3-directives/define/name-starts-with-percent.fail.6502
new file mode 100644
index 0000000..f918606
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-percent.fail.6502
@@ -0,0 +1,2 @@
+\ Variable name can't start with %
+DEFINE "%a",13
diff --git a/test/3-directives/define/name-starts-with-percent.fail.gold.txt b/test/3-directives/define/name-starts-with-percent.fail.gold.txt
new file mode 100644
index 0000000..b1187eb
--- /dev/null
+++ b/test/3-directives/define/name-starts-with-percent.fail.gold.txt
@@ -0,0 +1 @@
+error: Invalid symbol name; must start with a letter
diff --git a/test/3-directives/define/redefine.fail.6502 b/test/3-directives/define/redefine.fail.6502
new file mode 100644
index 0000000..91750ef
--- /dev/null
+++ b/test/3-directives/define/redefine.fail.6502
@@ -0,0 +1,3 @@
+\ Can't redefine variables
+a = 12
+DEFINE "a",13
diff --git a/test/3-directives/define/redefine.fail.gold.txt b/test/3-directives/define/redefine.fail.gold.txt
new file mode 100644
index 0000000..0f21b65
--- /dev/null
+++ b/test/3-directives/define/redefine.fail.gold.txt
@@ -0,0 +1 @@
+error: Symbol already defined
diff --git a/test/testrunner.py b/test/testrunner.py
index 8ec3ef9..f4876c7 100644
--- a/test/testrunner.py
+++ b/test/testrunner.py
@@ -123,7 +123,7 @@ def run_test(beebasm, path, file_names, file_name):
         # Duplicate captured data on stdout
         sys.stdout.write(capture)
         with open(gold_txt, 'r') as gold_file:
-            gold = gold_file.read()
+            gold = gold_file.read().strip()
         print('Comparing beebasm output to', gold_txt, end = '')
         if capture.find(gold) != -1:
             print(' succeeded')
@@ -199,4 +199,3 @@ def parse_args():
 except TestFailure as e:
     print("FAILURE: " + e.args[0], file = original_stdout)
     sys.exit(1)
-