diff --git a/cstdlib/stdio.c b/cstdlib/stdio.c
index d416d99..756883a 100644
--- a/cstdlib/stdio.c
+++ b/cstdlib/stdio.c
@@ -9,6 +9,8 @@
 
 FILE *CStdOut;
 
+static int ZeroValue = 0;
+static int TRUEValue = 1;
 static int EOFValue = EOF;
 static int SEEK_SETValue = SEEK_SET;
 static int SEEK_CURValue = SEEK_CUR;
@@ -251,7 +253,7 @@ int StdioBasePrintf(struct ParseState *Parser, FILE *Stream, char *StrOut, int S
                     if (ShowType == &IntType)
                     {
                         /* show a signed integer */
-                        if (IS_INTEGER_NUMERIC(ThisArg))
+                        if (IS_NUMERIC_COERCIBLE(ThisArg))
                             StdioFprintfWord(&SOStream, OneFormatBuf, ExpressionCoerceUnsignedInteger(ThisArg));
                         else
                             StdioOutPuts("XXX", &SOStream);
@@ -259,7 +261,7 @@ int StdioBasePrintf(struct ParseState *Parser, FILE *Stream, char *StrOut, int S
                     else if (ShowType == &FPType)
                     {
                         /* show a floating point number */
-                        if (IS_FP(ThisArg))
+                        if (IS_NUMERIC_COERCIBLE(ThisArg))
                             StdioFprintfFP(&SOStream, OneFormatBuf, ExpressionCoerceFP(ThisArg));
                         else
                             StdioOutPuts("XXX", &SOStream);
@@ -681,6 +683,11 @@ void StdioSetupFunc(void)
     VariableDefinePlatformVar(NULL, "stdin", FilePtrType, (union AnyValue *)&stdinValue, FALSE);
     VariableDefinePlatformVar(NULL, "stdout", FilePtrType, (union AnyValue *)&stdoutValue, FALSE);
     VariableDefinePlatformVar(NULL, "stderr", FilePtrType, (union AnyValue *)&stderrValue, FALSE);
+
+    /* define NULL, TRUE and FALSE */
+    VariableDefinePlatformVar(NULL, "NULL", &IntType, (union AnyValue *)&ZeroValue, FALSE);
+    VariableDefinePlatformVar(NULL, "TRUE", &IntType, (union AnyValue *)&TRUEValue, FALSE);
+    VariableDefinePlatformVar(NULL, "FALSE", &IntType, (union AnyValue *)&ZeroValue, FALSE);
 }
 
 /* portability-related I/O calls */
diff --git a/tests/00_assignment.c b/tests/00_assignment.c
index b174ab0..62adcec 100644
--- a/tests/00_assignment.c
+++ b/tests/00_assignment.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 a = 42;
 printf("%d\n", a);
diff --git a/tests/01_comment.c b/tests/01_comment.c
index 6919b9e..d2b3ad9 100644
--- a/tests/01_comment.c
+++ b/tests/01_comment.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 printf("Hello\n");
 printf("Hello\n"); /* this is a comment */ printf("Hello\n");
 printf("Hello\n");
diff --git a/tests/02_printf.c b/tests/02_printf.c
index 4523acb..66eed98 100644
--- a/tests/02_printf.c
+++ b/tests/02_printf.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 printf("Hello world\n");
 
 int Count;
diff --git a/tests/03_struct.c b/tests/03_struct.c
index e7e7c1a..db62cc2 100644
--- a/tests/03_struct.c
+++ b/tests/03_struct.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 struct fred
 {
     int boris;
diff --git a/tests/04_for.c b/tests/04_for.c
index 4ce2257..046e473 100644
--- a/tests/04_for.c
+++ b/tests/04_for.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int Count;
 
 for (Count = 1; Count <= 10; Count++)
diff --git a/tests/05_array.c b/tests/05_array.c
index 02a2883..a70ac0a 100644
--- a/tests/05_array.c
+++ b/tests/05_array.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int Count;
 int Array[10];
 
diff --git a/tests/06_case.c b/tests/06_case.c
index 9791ea1..d7f883d 100644
--- a/tests/06_case.c
+++ b/tests/06_case.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int Count;
 
 for (Count = 0; Count < 4; Count++)
diff --git a/tests/07_function.c b/tests/07_function.c
index 7538945..e7c4fa7 100644
--- a/tests/07_function.c
+++ b/tests/07_function.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int myfunc(int x)
 {
     return x * x;
diff --git a/tests/08_while.c b/tests/08_while.c
index 19fae8c..bb990b3 100644
--- a/tests/08_while.c
+++ b/tests/08_while.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int p;
 int t;
diff --git a/tests/09_do_while.c b/tests/09_do_while.c
index d9f63a7..adc4cae 100644
--- a/tests/09_do_while.c
+++ b/tests/09_do_while.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int p;
 int t;
diff --git a/tests/10_pointer.c b/tests/10_pointer.c
index 4206356..0e99787 100644
--- a/tests/10_pointer.c
+++ b/tests/10_pointer.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int *b;
 int c;
diff --git a/tests/11_precedence.c b/tests/11_precedence.c
index 954b7ef..7360312 100644
--- a/tests/11_precedence.c
+++ b/tests/11_precedence.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int b;
 int c;
diff --git a/tests/12_hashdefine.c b/tests/12_hashdefine.c
index e6278d9..680b87d 100644
--- a/tests/12_hashdefine.c
+++ b/tests/12_hashdefine.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 #define FRED 12
 #define BLOGGS(x) (12*(x))
 
diff --git a/tests/13_integer_literals.c b/tests/13_integer_literals.c
index be96c79..c0e99a1 100644
--- a/tests/13_integer_literals.c
+++ b/tests/13_integer_literals.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a = 24680;
 int b = 01234567;
 int c = 0x2468ac;
diff --git a/tests/14_if.c b/tests/14_if.c
index 6a1d43a..58dbed1 100644
--- a/tests/14_if.c
+++ b/tests/14_if.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a = 1;
 
 if (a)
diff --git a/tests/15_recursion.c b/tests/15_recursion.c
index d4926bb..766aa87 100644
--- a/tests/15_recursion.c
+++ b/tests/15_recursion.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int factorial(int i) 
 {
     if (i < 2)
diff --git a/tests/16_nesting.c b/tests/16_nesting.c
index c239aa3..520777e 100644
--- a/tests/16_nesting.c
+++ b/tests/16_nesting.c
@@ -1,12 +1,14 @@
-int x, y, z;
-
-for (x = 0; x < 2; x++)
-{
-    for (y = 0; y < 3; y++)
-    {
-        for (z = 0; z < 3; z++)
-        {
-            printf("%d %d %d\n", x, y, z);
-        }
-    }
-}
+#include <stdio.h>
+
+int x, y, z;
+
+for (x = 0; x < 2; x++)
+{
+    for (y = 0; y < 3; y++)
+    {
+        for (z = 0; z < 3; z++)
+        {
+            printf("%d %d %d\n", x, y, z);
+        }
+    }
+}
diff --git a/tests/17_enum.c b/tests/17_enum.c
index 08c865b..7d8cb61 100644
--- a/tests/17_enum.c
+++ b/tests/17_enum.c
@@ -1,20 +1,22 @@
-enum fred
-{
-    a,
-    b,
-    c,
-    d,
-    e = 54,
-    f = 73,
-    g,
-    h
-};
+#include <stdio.h>
+
+enum fred
+{
+    a,
+    b,
+    c,
+    d,
+    e = 54,
+    f = 73,
+    g,
+    h
+};
 
 enum fred frod;
-
-printf("%d %d %d %d %d %d %d %d\n", a, b, c, d, e, f, g, h);
-printf("%d\n", frod);
-frod = 12;
-printf("%d\n", frod);
-frod = e;
-printf("%d\n", frod);
+
+printf("%d %d %d %d %d %d %d %d\n", a, b, c, d, e, f, g, h);
+printf("%d\n", frod);
+frod = 12;
+printf("%d\n", frod);
+frod = e;
+printf("%d\n", frod);
diff --git a/tests/18_include.c b/tests/18_include.c
index 3438b07..0f14569 100644
--- a/tests/18_include.c
+++ b/tests/18_include.c
@@ -1,3 +1,5 @@
-printf("including\n");
-#include "18_include.h"
-printf("done\n");
+#include <stdio.h>
+
+printf("including\n");
+#include "18_include.h"
+printf("done\n");
diff --git a/tests/19_pointer_arithmetic.c b/tests/19_pointer_arithmetic.c
index a85d1e1..149edc4 100644
--- a/tests/19_pointer_arithmetic.c
+++ b/tests/19_pointer_arithmetic.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int *b;
 int *c;
diff --git a/tests/20_pointer_comparison.c b/tests/20_pointer_comparison.c
index 9561ac9..6977118 100644
--- a/tests/20_pointer_comparison.c
+++ b/tests/20_pointer_comparison.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a;
 int b;
 int *d;
diff --git a/tests/21_char_array.c b/tests/21_char_array.c
index c484f93..c21e5ca 100644
--- a/tests/21_char_array.c
+++ b/tests/21_char_array.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int x = 'a';
 char y = x;
 
diff --git a/tests/22_floating_point.c b/tests/22_floating_point.c
index 7261abd..8c6b394 100644
--- a/tests/22_floating_point.c
+++ b/tests/22_floating_point.c
@@ -1,40 +1,43 @@
-// variables
-float a = 12.34 + 56.78;
-printf("%f\n", a);
-
-// infix operators
-printf("%f\n", 12.34 + 56.78);
-printf("%f\n", 12.34 - 56.78);
-printf("%f\n", 12.34 * 56.78);
-printf("%f\n", 12.34 / 56.78);
-
-// comparison operators
-printf("%d %d %d %d %d %d\n", 12.34 < 56.78, 12.34 <= 56.78, 12.34 == 56.78, 12.34 >= 56.78, 12.34 > 56.78, 12.34 != 56.78);
-printf("%d %d %d %d %d %d\n", 12.34 < 12.34, 12.34 <= 12.34, 12.34 == 12.34, 12.34 >= 12.34, 12.34 > 12.34, 12.34 != 12.34);
-printf("%d %d %d %d %d %d\n", 56.78 < 12.34, 56.78 <= 12.34, 56.78 == 12.34, 56.78 >= 12.34, 56.78 > 12.34, 56.78 != 12.34);
-
-// assignment operators
-a = 12.34;
-a += 56.78;
-printf("%f\n", a);
-
-a = 12.34;
-a -= 56.78;
-printf("%f\n", a);
-
-a = 12.34;
-a *= 56.78;
-printf("%f\n", a);
-
-a = 12.34;
-a /= 56.78;
-printf("%f\n", a);
-
-// prefix operators
-printf("%f\n", +12.34);
-printf("%f\n", -12.34);
-
-// type coercion
-a = 2;
-printf("%f\n", a);
-printf("%f\n", sin(2));
+#include <stdio.h>
+#include <math.h>
+
+// variables
+float a = 12.34 + 56.78;
+printf("%f\n", a);
+
+// infix operators
+printf("%f\n", 12.34 + 56.78);
+printf("%f\n", 12.34 - 56.78);
+printf("%f\n", 12.34 * 56.78);
+printf("%f\n", 12.34 / 56.78);
+
+// comparison operators
+printf("%d %d %d %d %d %d\n", 12.34 < 56.78, 12.34 <= 56.78, 12.34 == 56.78, 12.34 >= 56.78, 12.34 > 56.78, 12.34 != 56.78);
+printf("%d %d %d %d %d %d\n", 12.34 < 12.34, 12.34 <= 12.34, 12.34 == 12.34, 12.34 >= 12.34, 12.34 > 12.34, 12.34 != 12.34);
+printf("%d %d %d %d %d %d\n", 56.78 < 12.34, 56.78 <= 12.34, 56.78 == 12.34, 56.78 >= 12.34, 56.78 > 12.34, 56.78 != 12.34);
+
+// assignment operators
+a = 12.34;
+a += 56.78;
+printf("%f\n", a);
+
+a = 12.34;
+a -= 56.78;
+printf("%f\n", a);
+
+a = 12.34;
+a *= 56.78;
+printf("%f\n", a);
+
+a = 12.34;
+a /= 56.78;
+printf("%f\n", a);
+
+// prefix operators
+printf("%f\n", +12.34);
+printf("%f\n", -12.34);
+
+// type coercion
+a = 2;
+printf("%f\n", a);
+printf("%f\n", sin(2));
diff --git a/tests/22_floating_point.expect b/tests/22_floating_point.expect
index 818379d..282d089 100644
--- a/tests/22_floating_point.expect
+++ b/tests/22_floating_point.expect
@@ -1,16 +1,16 @@
-69.12
-69.12
--44.44
-700.6652
+69.120000
+69.120000
+-44.440000
+700.665200
 0.217330
 1 1 0 0 0 1
 0 1 1 1 0 0
 0 0 0 1 1 1
-69.12
--44.44
-700.6652
+69.120000
+-44.440000
+700.665200
 0.217330
-12.34
--12.34
-2.0
+12.340000
+-12.340000
+2.000000
 0.909297
diff --git a/tests/23_type_coercion.c b/tests/23_type_coercion.c
index 2c1ea8b..7070cc2 100644
--- a/tests/23_type_coercion.c
+++ b/tests/23_type_coercion.c
@@ -1,45 +1,47 @@
-void charfunc(char a)
-{
-    printf("char: %c\n", a);
-}
-
-void intfunc(int a)
-{
-    printf("int: %d\n", a);
-}
-
-void floatfunc(float a)
-{
-    printf("float: %f\n", a);
-}
-
-charfunc('a');
-charfunc(98);
-charfunc(99.0);
-
-intfunc('a');
-intfunc(98);
-intfunc(99.0);
-
-floatfunc('a');
-floatfunc(98);
-floatfunc(99.0);
-
-printf("%c %d %f\n", 'a', 'b', 'c');
-printf("%c %d %f\n", 97, 98, 99);
-printf("%c %d %f\n", 97.0, 98.0, 99.0);
-
-char b = 97;
-char c = 97.0;
-
-printf("%d %d\n", b, c);
-
-int d = 'a';
-int e = 97.0;
-
-printf("%d %d\n", d, e);
-
-float f = 'a';
-float g = 97;
-
-printf("%f %f\n", f, g);
+#include <stdio.h>
+
+void charfunc(char a)
+{
+    printf("char: %c\n", a);
+}
+
+void intfunc(int a)
+{
+    printf("int: %d\n", a);
+}
+
+void floatfunc(float a)
+{
+    printf("float: %f\n", a);
+}
+
+charfunc('a');
+charfunc(98);
+charfunc(99.0);
+
+intfunc('a');
+intfunc(98);
+intfunc(99.0);
+
+floatfunc('a');
+floatfunc(98);
+floatfunc(99.0);
+
+printf("%c %d %f\n", 'a', 'b', 'c');
+printf("%c %d %f\n", 97, 98, 99);
+printf("%c %d %f\n", 97.0, 98.0, 99.0);
+
+char b = 97;
+char c = 97.0;
+
+printf("%d %d\n", b, c);
+
+int d = 'a';
+int e = 97.0;
+
+printf("%d %d\n", d, e);
+
+float f = 'a';
+float g = 97;
+
+printf("%f %f\n", f, g);
diff --git a/tests/23_type_coercion.expect b/tests/23_type_coercion.expect
index a9fb610..a4c5b68 100644
--- a/tests/23_type_coercion.expect
+++ b/tests/23_type_coercion.expect
@@ -1,15 +1,15 @@
-char: a
-char: b
-char: c
-int: 97
-int: 98
-int: 99
-float: 97.0
-float: 98.0
-float: 99.0
-a 98 99.0
-a 98 99.0
-a 98 99.0
-97 97
-97 97
-97.0 97.0
+char: a
+char: b
+char: c
+int: 97
+int: 98
+int: 99
+float: 97.000000
+float: 98.000000
+float: 99.000000
+a 98 99.000000
+a 98 99.000000
+a 98 99.000000
+97 97
+97 97
+97.000000 97.000000
diff --git a/tests/24_math_library.c b/tests/24_math_library.c
index 1f69a30..88fd817 100644
--- a/tests/24_math_library.c
+++ b/tests/24_math_library.c
@@ -1,3 +1,6 @@
+#include <stdio.h>
+#include <math.h>
+
 printf("%f\n", sin(0.12));
 printf("%f\n", cos(0.12));
 printf("%f\n", tan(0.12));
diff --git a/tests/24_math_library.expect b/tests/24_math_library.expect
index c08711d..99f7299 100644
--- a/tests/24_math_library.expect
+++ b/tests/24_math_library.expect
@@ -1,18 +1,18 @@
 0.119712
-0.992808
+0.992809
 0.120579
-0.120289
+0.120290
 1.450506
-0.119428
+0.119429
 0.120288
-1.007208
+1.007209
 0.119427
-1.127496
-0.12
--2.120263
--0.920818
+1.127497
+0.120000
+-2.120264
+-0.920819
 0.775357
 0.346410
-12.0
-13.0
-12.0
+12.000000
+13.000000
+12.000000
diff --git a/tests/25_quicksort.c b/tests/25_quicksort.c
index ada436d..922fd41 100644
--- a/tests/25_quicksort.c
+++ b/tests/25_quicksort.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int array[16];
 
 //Swap integer values by array indexes
diff --git a/tests/26_character_constants.c b/tests/26_character_constants.c
index 4f40b77..5674b88 100644
--- a/tests/26_character_constants.c
+++ b/tests/26_character_constants.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 printf("%d\n", '\1');
 printf("%d\n", '\10');
 printf("%d\n", '\100');
diff --git a/tests/27_sizeof.c b/tests/27_sizeof.c
index 875e3d5..e6a20fd 100644
--- a/tests/27_sizeof.c
+++ b/tests/27_sizeof.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 char a;
 int b;
 double c;
diff --git a/tests/28_strings.c b/tests/28_strings.c
index 46f886c..8ec7fc3 100644
--- a/tests/28_strings.c
+++ b/tests/28_strings.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 char a[10];
 
 strcpy(a, "hello");
diff --git a/tests/29_array_address.c b/tests/29_array_address.c
index 83f63ed..b81ce89 100644
--- a/tests/29_array_address.c
+++ b/tests/29_array_address.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 char a[10];
 strcpy(a, "abcdef");
 printf("%s\n", &a[1]);
diff --git a/tests/34_array_assignment.c b/tests/34_array_assignment.c
index 1d2d5b0..4e096cd 100644
--- a/tests/34_array_assignment.c
+++ b/tests/34_array_assignment.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a[4];
 
 a[0] = 12;
diff --git a/tests/35_sizeof.c b/tests/35_sizeof.c
index 70ae64e..7b27af0 100644
--- a/tests/35_sizeof.c
+++ b/tests/35_sizeof.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 char a;
 short b;
 
diff --git a/tests/36_array_initialisers.c b/tests/36_array_initialisers.c
index 8b84ae7..7ff386a 100644
--- a/tests/36_array_initialisers.c
+++ b/tests/36_array_initialisers.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int Count;
 
 int Array[10] = { 12, 34, 56, 78, 90, 123, 456, 789, 8642, 9753 };
diff --git a/tests/37_sprintf.c b/tests/37_sprintf.c
index c9ba3a5..4d8aa67 100644
--- a/tests/37_sprintf.c
+++ b/tests/37_sprintf.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 char Buf[100];
 int Count;
 
diff --git a/tests/38_multiple_array_index.c b/tests/38_multiple_array_index.c
index d6f9092..dbb32e9 100644
--- a/tests/38_multiple_array_index.c
+++ b/tests/38_multiple_array_index.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 int a[4][4];
 int b = 0;
 int x;
diff --git a/tests/39_typedef.c b/tests/39_typedef.c
index 541a493..60d37ec 100644
--- a/tests/39_typedef.c
+++ b/tests/39_typedef.c
@@ -1,3 +1,5 @@
+#include <stdio.h>
+
 typedef int MyInt;
 
 MyInt a = 1;