diff --git a/curs/chap-04-reprezentare/01-data-interp/.gitignore b/curs/chap-04-reprezentare/01-data-interp/.gitignore
new file mode 100644
index 00000000..7d08180b
--- /dev/null
+++ b/curs/chap-04-reprezentare/01-data-interp/.gitignore
@@ -0,0 +1 @@
+/data_interp
diff --git a/curs/chap-04-reprezentare/01-data-interp/Makefile b/curs/chap-04-reprezentare/01-data-interp/Makefile
new file mode 100644
index 00000000..113b10dc
--- /dev/null
+++ b/curs/chap-04-reprezentare/01-data-interp/Makefile
@@ -0,0 +1,13 @@
+CFLAGS = -m32 -fno-PIC -Wall
+LDFLAGS = -m32 -no-pie
+
+.PHONY: all clean
+
+all: data_interp
+
+data_interp: data_interp.o
+
+data_interp.o: data_interp.c
+
+clean:
+	-rm -f *~ data_interp.o data_interp
diff --git a/curs/chap-04-reprezentare/01-data-interp/data_interp.c b/curs/chap-04-reprezentare/01-data-interp/data_interp.c
new file mode 100644
index 00000000..e3fd05d1
--- /dev/null
+++ b/curs/chap-04-reprezentare/01-data-interp/data_interp.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+unsigned char char_array[8] = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88};
+unsigned short short_array[4];
+unsigned int int_array[2];
+unsigned long long ll_array[1];
+
+int main(void)
+{
+	size_t j;
+
+	memcpy(short_array, char_array, sizeof(char_array));
+	memcpy(int_array, char_array, sizeof(char_array));
+	memcpy(ll_array, char_array, sizeof(char_array));
+
+	printf("s:");
+	for (j = 0; j < sizeof(short_array) / sizeof(short_array[0]); j++)
+		printf(" 0x%04x", short_array[j]);
+	printf("\n");
+
+	printf("i:");
+	for (j = 0; j < sizeof(int_array) / sizeof(int_array[0]); j++)
+		printf(" 0x%08x", int_array[j]);
+	printf("\n");
+
+	printf("ll:");
+	for (j = 0; j < sizeof(ll_array) / sizeof(ll_array[0]); j++)
+		printf(" 0x%016llx", ll_array[j]);
+	printf("\n");
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/02-same-data/.gitignore b/curs/chap-04-reprezentare/02-same-data/.gitignore
new file mode 100644
index 00000000..297dbd6d
--- /dev/null
+++ b/curs/chap-04-reprezentare/02-same-data/.gitignore
@@ -0,0 +1 @@
+/same_data
diff --git a/curs/chap-04-reprezentare/02-same-data/Makefile b/curs/chap-04-reprezentare/02-same-data/Makefile
new file mode 100644
index 00000000..ed3c5503
--- /dev/null
+++ b/curs/chap-04-reprezentare/02-same-data/Makefile
@@ -0,0 +1,13 @@
+CFLAGS = -m32 -fno-PIC -Wall
+LDFLAGS = -m32 -no-pie
+
+.PHONY: all clean
+
+all: same_data
+
+same_data: same_data.o
+
+same_data.o: same_data.c
+
+clean:
+	-rm -f *~ same_data.o same_data
diff --git a/curs/chap-04-reprezentare/02-same-data/same_data.c b/curs/chap-04-reprezentare/02-same-data/same_data.c
new file mode 100644
index 00000000..5af24133
--- /dev/null
+++ b/curs/chap-04-reprezentare/02-same-data/same_data.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+
+unsigned int i = 0x12345678;
+unsigned short int s[2] = {0x5678, 0x1234};
+unsigned char c[4] = {0x78, 0x56, 0x34, 0x12};
+
+static void dump(const void *start, size_t len, const char *id)
+{
+	unsigned int i;
+
+	printf("\nDumping %s from address %p (%zu bytes):\n", id, start, len);
+	for (i = 0; i < len; i++) {
+		/* Add a newline every 8 bytes. */
+		if (i % 8 == 0)
+			printf("\n");
+		printf(" %02x", *((const unsigned char *) start + i));
+	}
+	/* And newline at the end. */
+	printf("\n");
+}
+
+
+int main(void)
+{
+	dump(&i, sizeof(i), "i (unsigned int)");
+	dump(&s, sizeof(s), "s (unsigned short int)");
+	dump(&c, sizeof(c), "c (unsigned char)");
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/03-signed-unsigned/.gitignore b/curs/chap-04-reprezentare/03-signed-unsigned/.gitignore
new file mode 100644
index 00000000..483a55ac
--- /dev/null
+++ b/curs/chap-04-reprezentare/03-signed-unsigned/.gitignore
@@ -0,0 +1 @@
+/signed_unsigned
diff --git a/curs/chap-04-reprezentare/03-signed-unsigned/Makefile b/curs/chap-04-reprezentare/03-signed-unsigned/Makefile
new file mode 100644
index 00000000..b50036c0
--- /dev/null
+++ b/curs/chap-04-reprezentare/03-signed-unsigned/Makefile
@@ -0,0 +1,13 @@
+CFLAGS = -m32 -fno-PIC -Wall
+LDFLAGS = -m32 -no-pie
+
+.PHONY: all clean
+
+all: signed_unsigned
+
+signed_unsigned: signed_unsigned.o
+
+signed_unsigned.o: signed_unsigned.c
+
+clean:
+	-rm -f *~ signed_unsigned.o signed_unsigned
diff --git a/curs/chap-04-reprezentare/03-signed-unsigned/signed_unsigned.c b/curs/chap-04-reprezentare/03-signed-unsigned/signed_unsigned.c
new file mode 100644
index 00000000..77a1617a
--- /dev/null
+++ b/curs/chap-04-reprezentare/03-signed-unsigned/signed_unsigned.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+
+unsigned char unsigned_char = 0xaa;
+signed char signed_char = 0xaa;
+
+short int short_int = -1;
+unsigned int unsigned_int;
+
+int main(void)
+{
+	printf("%hhu, %hhd\n", unsigned_char, signed_char);
+
+	unsigned_int = short_int;
+	printf("short_int (%p): 0x%08x, short_int: %u, short_int: %d\n", &short_int, short_int, short_int, short_int);
+	printf("unsigned_int (%p): 0x%08x, unsigned_int: %u, unsigned_int: %d\n", &unsigned_int, unsigned_int, unsigned_int, unsigned_int);
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/01-endianness/.gitignore b/curs/chap-04-reprezentare/04-endianess/.gitignore
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/.gitignore
rename to curs/chap-04-reprezentare/04-endianess/.gitignore
diff --git a/curs/chap-04-reprezentare/01-endianness/Makefile b/curs/chap-04-reprezentare/04-endianess/Makefile
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/Makefile
rename to curs/chap-04-reprezentare/04-endianess/Makefile
diff --git a/curs/chap-04-reprezentare/04-endianess/README b/curs/chap-04-reprezentare/04-endianess/README
new file mode 100644
index 00000000..4c1bac37
--- /dev/null
+++ b/curs/chap-04-reprezentare/04-endianess/README
@@ -0,0 +1,24 @@
+# curs-04-demo
+
+
+1. Laborator 1, exercițiu 5, mem.c 
+- se printează octet cu octet conținutul fiecărei variabile
+- observați adresele de început pentru variabile
+- observati adresele fiecărui octet component
+- reconstituiți valoarea variabilei folosind octeții si aritmetica în baza 16
+
+2. endian.asm
+- compilați si încărcati în gdb
+ make
+ gdb endian
+ b main
+ r
+- examinați variabilele a, b, c
+- octet cu octet cu comanda în gdb:  x/20xb &a
+- short cu short cu comanda în gdb:  x/20xh &a
+- word cu word cu comanda în gdb:  x/20xw &a
+- idem pentru varianbilele b, c
+
+
+
+
diff --git a/curs/chap-04-reprezentare/01-endianness/README.md b/curs/chap-04-reprezentare/04-endianess/README.md
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/README.md
rename to curs/chap-04-reprezentare/04-endianess/README.md
diff --git a/curs/chap-04-reprezentare/01-endianness/bin-oct-hex.c b/curs/chap-04-reprezentare/04-endianess/bin-oct-hex.c
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/bin-oct-hex.c
rename to curs/chap-04-reprezentare/04-endianess/bin-oct-hex.c
diff --git a/curs/chap-04-reprezentare/01-endianness/endian.asm b/curs/chap-04-reprezentare/04-endianess/endian.asm
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/endian.asm
rename to curs/chap-04-reprezentare/04-endianess/endian.asm
diff --git a/curs/chap-04-reprezentare/01-endianness/mem.c b/curs/chap-04-reprezentare/04-endianess/mem.c
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/mem.c
rename to curs/chap-04-reprezentare/04-endianess/mem.c
diff --git a/curs/chap-04-reprezentare/01-endianness/print_code.c b/curs/chap-04-reprezentare/04-endianess/print_code.c
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/print_code.c
rename to curs/chap-04-reprezentare/04-endianess/print_code.c
diff --git a/curs/chap-04-reprezentare/01-endianness/signed-unsigned.c b/curs/chap-04-reprezentare/04-endianess/signed-unsigned.c
similarity index 100%
rename from curs/chap-04-reprezentare/01-endianness/signed-unsigned.c
rename to curs/chap-04-reprezentare/04-endianess/signed-unsigned.c
diff --git a/curs/chap-04-reprezentare/02-endianness/Makefile b/curs/chap-04-reprezentare/05-endianess/Makefile
similarity index 100%
rename from curs/chap-04-reprezentare/02-endianness/Makefile
rename to curs/chap-04-reprezentare/05-endianess/Makefile
diff --git a/curs/chap-04-reprezentare/02-endianness/endianess.c b/curs/chap-04-reprezentare/05-endianess/endianess.c
similarity index 100%
rename from curs/chap-04-reprezentare/02-endianness/endianess.c
rename to curs/chap-04-reprezentare/05-endianess/endianess.c
diff --git a/curs/chap-04-reprezentare/02-endianness/endianess2.c b/curs/chap-04-reprezentare/05-endianess/endianess2.c
similarity index 100%
rename from curs/chap-04-reprezentare/02-endianness/endianess2.c
rename to curs/chap-04-reprezentare/05-endianess/endianess2.c
diff --git a/curs/chap-04-reprezentare/06-C2/.gitignore b/curs/chap-04-reprezentare/06-C2/.gitignore
new file mode 100644
index 00000000..0eeecc13
--- /dev/null
+++ b/curs/chap-04-reprezentare/06-C2/.gitignore
@@ -0,0 +1,6 @@
+/f.dat
+/g.dat
+/endianess
+/endianess2
+/print_flags
+/flags
diff --git a/curs/chap-04-reprezentare/03-C2/Makefile b/curs/chap-04-reprezentare/06-C2/Makefile
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/Makefile
rename to curs/chap-04-reprezentare/06-C2/Makefile
diff --git a/curs/chap-04-reprezentare/03-C2/README.md b/curs/chap-04-reprezentare/06-C2/README.md
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/README.md
rename to curs/chap-04-reprezentare/06-C2/README.md
diff --git a/curs/chap-04-reprezentare/03-C2/abs.cpp b/curs/chap-04-reprezentare/06-C2/abs.cpp
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/abs.cpp
rename to curs/chap-04-reprezentare/06-C2/abs.cpp
diff --git a/curs/chap-04-reprezentare/03-C2/asymmetrical.c b/curs/chap-04-reprezentare/06-C2/asymmetrical.c
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/asymmetrical.c
rename to curs/chap-04-reprezentare/06-C2/asymmetrical.c
diff --git a/curs/chap-04-reprezentare/03-C2/do_not_mix.c b/curs/chap-04-reprezentare/06-C2/do_not_mix.c
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/do_not_mix.c
rename to curs/chap-04-reprezentare/06-C2/do_not_mix.c
diff --git a/curs/chap-04-reprezentare/03-C2/flags.asm b/curs/chap-04-reprezentare/06-C2/flags.asm
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/flags.asm
rename to curs/chap-04-reprezentare/06-C2/flags.asm
diff --git a/curs/chap-04-reprezentare/03-C2/print_flags.c b/curs/chap-04-reprezentare/06-C2/print_flags.c
similarity index 100%
rename from curs/chap-04-reprezentare/03-C2/print_flags.c
rename to curs/chap-04-reprezentare/06-C2/print_flags.c
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/.gitignore b/curs/chap-04-reprezentare/07-signed-unsigned-ops/.gitignore
new file mode 100644
index 00000000..22f41a0a
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/.gitignore
@@ -0,0 +1,4 @@
+/cast_op_precedence
+/negative_overflow
+/signed_unsigned_print
+/signed_unsigned_char_int
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/Makefile b/curs/chap-04-reprezentare/07-signed-unsigned-ops/Makefile
new file mode 100644
index 00000000..60e32886
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/Makefile
@@ -0,0 +1,14 @@
+CFLAGS = -m32 -fno-PIC -Wall
+LDFLAGS = -m32 -no-pie
+BINARIES = cast_op_precedence signed_unsigned_char_int signed_unsigned_print negative_overflow
+
+.PHONY: all clean
+
+all: $(BINARIES)
+
+$(BINARIES): %: %.o
+
+: %.o: %.c
+
+clean:
+	-rm -f *~ $(BINARIES) $(BINARIES:=.o)
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/cast_op_precedence.c b/curs/chap-04-reprezentare/07-signed-unsigned-ops/cast_op_precedence.c
new file mode 100644
index 00000000..6382e711
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/cast_op_precedence.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int main(void)
+{
+  signed int a, b, c, d;
+  signed char c1 = 100, c2 = 100, c3, c4 = 127, c5 = 127, c6;
+
+	c3 = c1 + c2;
+	a = c3;
+	b = c1 + c2;
+
+	printf("a: 0x%08x\n", a);
+	printf("b: 0x%08x\n", b);
+
+	c6 = ++c4;
+	c = c6;
+	d = ++c5;
+
+	printf("c: 0x%08x\n", c);
+	printf("d: 0x%08x\n", d);
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/negative_overflow.c b/curs/chap-04-reprezentare/07-signed-unsigned-ops/negative_overflow.c
new file mode 100644
index 00000000..07aa17fc
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/negative_overflow.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main(void)
+{
+	signed char c = -120;
+	unsigned char cu = c;
+
+	printf("0x%02x\n", c);
+	printf("0x%02x\n", cu);
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_char_int.c b/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_char_int.c
new file mode 100644
index 00000000..f03e83f3
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_char_int.c
@@ -0,0 +1,38 @@
+#include <stdio.h>
+
+int main(void)
+{
+	signed char c1 = -9;
+	unsigned char c2 = c1;
+	signed int i1;
+	unsigned int i2;
+
+	i1 = c1;
+	printf("0x%08x\n", i1);
+	i1 = c2;
+	printf("0x%08x\n", i1);
+	i1 = c1 + c2;
+	printf("0x%08x\n", i1);
+
+	i2 = c1;
+	printf("0x%08x\n", i2);
+	i2 = c2;
+	printf("0x%08x\n", i2);
+	i2 = c1 + c2;
+	printf("0x%08x\n", i2);
+
+	i1 = -9;
+	i2 = i1;
+
+	c1 = i1;
+	printf("0x%02x\n", c1);
+	c1 = i2;
+	printf("0x%02x\n", c1);
+
+	c2 = i1;
+	printf("0x%02x\n", c2);
+	c2 = i2;
+	printf("0x%02x\n", c2);
+
+	return 0;
+}
diff --git a/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_print.c b/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_print.c
new file mode 100644
index 00000000..9a23faa2
--- /dev/null
+++ b/curs/chap-04-reprezentare/07-signed-unsigned-ops/signed_unsigned_print.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+
+int v1 = -1;
+unsigned int v2 = -2;
+
+int sum1;
+unsigned int sum2;
+
+int main(void)
+{
+	printf("v1 (%%d): %d, v1 (%%u): %u, v1 (%%08x): 0x:%08x\n", v1, v1, v1);
+	printf("v2 (%%d): %d, v2 (%%u): %u, v2 (%%08x): 0x:%08x\n", v2, v2, v2);
+	printf("-1 (%%d): %d, -1 (%%u): %u, -1 (%%08x): 0x:%08x\n", -1, -1, -1);
+
+	sum1 = v1 + 20;
+	sum2 = v2 + 20;
+
+	printf("sum1 (%%d): %d, sum1 (%%u): %u, sum1 (%%08x): 0x:%08x\n", sum1, sum1, sum1);
+	printf("sum2 (%%d): %d, sum2 (%%u): %u, sum2 (%%08x): 0x:%08x\n", sum2, sum2, sum2);
+
+	// MAXINT MAXINT-1
+	if (v1 < v2)
+		printf("-1 < -2\n");
+	else
+		printf("-1 > -2\n");
+
+	//10      MAXINT-1
+	v1 = 10;
+	if (v1 < v2)
+		printf("10 < -2\n");
+	else
+		printf("10 > -2\n");
+
+	return 0;
+}